exactly - but neither does it say they have to have those Flaws... what it does say is that Age Quickly, and Susceptible To Deprivation are indeed Flaws, worth points, and "optional" in the sense that you (the saga) choose to design them in, or not.
I still don't see the problem. If Aging and Susceptability to Deprivation were the default for magical creatures, people would be complaining because ghostly characters have to buy the Virtues Immune to Deprivation and Unaging.
Just because the default for ALL Magical creatures is one way or the other, doesn't prevent the troupe from saying the default should be different for some subset of Magic creatures. All this wailing and gnashing of teeth is unwarranted. If your troupe wants one set of Flaws or Virtues to be part of the standard template for a set of Magic creatures go ahead. The rules allow for it.
No offense, but I loathe that argument. There's nothing published in ANY rule book that can't be changed to suit your saga. House rules always trump book rules. Period. End of story.
Pointing out you can houserule something you don't like contributes nothing to the discussion, imho. Everyone is fully aware of that. Everyone also seems to be under the impression that future Ars products are going to assume that immortality is the default state for magical critters. So we are discussing the implications of these rules as written.
I'm pretty sure what I'm going to do with these rules. What I am trying to get from this thread is an idea of what other people are going to do and, in particular, what the official line in the future is likely to be and the implications of that for the game world.
Familiars are different. The way you and your familiar share known languages is one example, go by the core book and don't worry about it unless your starting a new game (or no one has a familiar yet)
I just wanted to point out that I myself have not bothered with a Familiar ever since 5th edition. The Familiar rules are, well, no offense, they are lame. I can only enchant the bond with effects that affect the Familiar that I control, or effects that affect me that he controls. Yes, I can MuAn some powers (though there are no guidelines for this, it just says "Level 25, transform into a magical creature"). But this is still weak compared to the old way, with the Bond Qualities and such that could grant powers the familiar could use at will and affect others with.
Here is an idea. Bring back Bond Qualities (and add Inferiorities); minor and major, 3 points or 10 points. Arcane Lore and such could e a BBond Quality. Mortality could be an Inferiority. Retaining Immortality could beb a Quality, and being Independantly minded could be a required Inferiority. A better than normal learning ability could e a quality (better than other creatures with might in that they are not penalized), with the fiat that this learning must be recieved from the magus it is bonded with.
I did just now, and that is also a good idea 
No offense, but I loathe the argument that "book X didn't follow my interpretation of the core rules, therefore my game is broken, now I'm going to whine incessantly, even though the rules in book X easily allow for a fix that will obviate my concerns." If proposing house rules, which allow you to continue to play your saga the way you want doesn't contribute to the discussion, then what's the point of the discussion? Whining for the sake of whining? Whining about the rules, and then ignoring proposed house rules, is just about as pointless as it gets.
All Divine creatures are unaging. All Infernal creatures are unaging. Everything I've ever read suggests all Faerie creatures are unaging. Why do you think the default for Magical creatures should be any different?
If it makes you feel better, I think that the RoP Magic rules are fine just the way they are. But, if it makes people feel better, I say let them whine and complain. I have done it, I needed to do it, and it ideed helped me learn and adapt. And I agree with both of you to a degree. Saying you can "HR (something)" as a rhetorical form of defense really doesn't help, but at the same time, ignoring all suggested Hs also doesn't help. Part of the purpose of these sorts of discussions is to gauge what the community thinks about "rule X", discover some of the intent behind "rule x", see what HR's others (who are not the author) suggest &/or are using, and the to use all of this in order to make a more informed decision.
And, even though I myself am not understanding the full degree of the complaint (as I said, I think the RoP Magic rules are fine), it helps people to vent and whine. They will eventually adapt. I have. I know that it isn't fair either. The authors are also fans of the game. You put a lot of effort and emotion into your creation, hoping to contribute something important and lasting to the game. And you have! RoP-Magic is the breakthrough book of 5th edition, as much as Mytsteries was for 4th.
Contributing to this game probably means much much more to you than whatever compensation you recieve (I was told you guys get paid with more books ), and it probably hurts to have your babby criticized so. But it comes with the territory. You should know that by now, and I reccomend you get thicker skin. Do know, however, that there are fans out there, old timer fans, that really admire and appreciate this book. I can no longer envision playing the game proper without it. It has become an essential core book almost overnight.
I should have pointed this out earlier, but the magical creatures aren't my rules. I created some creatures using the rules, but didn't write them. In fact during the writing process, I argued that Susceptability to Deprivation should be the default. 
I had completely forgotten about that until just now. I guess Erik did a better job of convincing me than I remembered.
My beef with the line of argument is that when you set a default you have to make choices. I think unaging and immune to deprivation are the right default choices for Magic creatures. I think some subsets of magical creatures should have the Susceptible to Deprivation Flaw. In fact, I think I gave it to all the animals I created. I don't think all animals should have Ages Quickly Flaw, but some should. I think it's perfectly appropriate for relatively low level creatures. But when you think of all the magical creatures: elementals, ghosts, place spirits, etc. that are unaging, setting the default to aging doesn't make sense to me. Even dragons, do they die of old age? No. They become less and less active, but I don't recall any stories of magical animals dying of old age.
People's primary complaint about this choice seems to be that it changes their preconceived notions about familiars. Well, nothing in RoP: Magic says that all potential familiars have to be immune to aging and deprivation. The troupe/storyguide creates the potential familiars for his or her game. In your saga you can decide that all Magic critters that are potential familiars have the Age Quickly and Susceptible to Deprivation Flaws. There is nothing in the rules that prevents you from doing it.
When we initially used the rules from this book, this subject was a pretty contentious one for our group, and we hashed over it pretty extensively before deciding that we quite liked it.
Requiring the consumption of vis to grow and limiting advancement totals for magical animal companions and familiars is a real change to how we had been playing. At the same time, the approach that we used before (advancing these beings as companions/grogs) was also routinely contentious in our games.
The preexisting argument in our troupe was based on the question "Are you entitled to a 'strap-on character' thanks to the Magical Animal Companion story flaw?" Note that this is where almost all familiars in our games have started out, too. Animal companions and familiars tended to take full advantage of different advancement opportunities throughout the year: when a fellow player's maga spent a season in study, her squirrel familiar was in my scholar-companion's Magic Theory, Artes Liberales, or Philosophiae classes, or reading books to advance in its own right. And so on. This approach translated into a perceived munchkiny power shift, and we argued back and forth over whether this was alright, whether to houserule limitations to the process or ban magical animals from play for awhile.
Once we sorted out different elements in the new Magic Realm material, we found that it solved a lot of these concerns and others. Our magi, in our troupe, tend to be Vis-hoarders. The resulting stockpiles led to discussions of whether we should cut resource levels in our campaigns, etc etc. Now, the magical animals of the game need to ingest the stuff, adding to the ways in which we can use vis and makes it more precious once again. It is certainly possible to advance magical animals and companions, but the rate is slowed, somewhat, which has closed the books on our debates over them as being a "too easy" free advantage.
Some few faeries do age, which is one of the drivers of the changeling phenomenon: they can make themselves young again by being tended as a baby for a time. The rest seem ageless, yes, although some do die of natural causes, Pan for example, during the Silencing of the Oracles.
You find somewhere that I said the rules are broken? I said I didn't like them and I explained why.
My interest in this topic is precisely that future products could assume every little rabbit born in a magic aura ends up immortal. Or they could not work that way, because its a virtues/flaws sort of thing. I would like to convince the writers of a later bestiary or other book with magical animals in it that it only the big bad high Might creatures or those things that are spirits should be immortal by default.
But I guess feedback like that is whining. So noted.
That's not the rule in RoP: Magic. I tried to point out to you that it is the creator of the creature who decides whether a creature is immortal or not. The storyguide/troupe can give the creature Ages Quickly and Susceptible to Deprivation. This is not a house rule. It's accounted for in the rules as written. If all Magic creatures were immortal, there would be no need for either of these Flaws. You ignored this fact and continued to lambast the author for selecting the default for magical creatures as immortal and belittled my suggestion to alleve your problem as a "house rule."
I'm sorry if I offended you, but I don't see the point of arguing against this strawman construct. If you are going to ignore the rules and argue against something that isn't even required by the rules, that's just silly in my view.
You are right that its not /required/ that all creatures of magic be immortal. But its a flaw if they are not. The usual perception is that the default option does not include any particular flaw. As a result, it seemed likely to me that as written, future products would tend towards making magical creatures immortal. I don't recall seeing a section with guidelines on deciding what sorts of creatures ought to have what sorts of flaws or how common Ages Quickly is. Now you can say "that's up to the Storyguide", but the storyguide isn't the only one writing Ars Magica material. What's going to be the expectation in future Tribunal books, Bestiaries, Adventures, etc? I'm hoping not "totally haphazard" or "I guess its not immortal because I need more flaws".
Btw, I vehemently object to the suggestion I "lambasted" anyone. I have never said anything derogatory about another poster, author or otherwise. I don't know what posts you are reading, but they apparently aren't mine. I haven't even "attacked" this idea, unless you think 'I'll probably do it differently' is some sort of scathing onslaught. Even the supposed attack of mine you quoted (which wasn't an attack) was followed immediately by me saying "so I'll just set 'ages quickly' as the default in my campaign".
I don't get what you are reacting to. I already said... before you brought it up... that I was going to handle it in my saga the way you later suggested. What I'm trying to discuss is what is the general consensus....or even better (albeit unlikely)... the Line's official view of how things are envisioned.
The line's official view is up to David, who is off at Grand Tribunal UK, I hear.
I know. Even if David was sitting around staring at the forums all day, I wouldn't actually expect him to make a hard answer to the question. Pleasantly surprising, but certainly not expected. All I was expecting to get was some sort of discussion of the membership on the topic of how people thought it should be handled.
I've been out of this conversation for a long time (just ben busy). But My point was what I said in the last line "The core was written before the relationship between immortality and might became established"
The intention of the familiars rules was to take a creature with might and extend its life to be as log as the life of the magus.
Things have changed since then.
Ok... Just to be a jerk
If the default was that magical creatures were mortal, with immortality being a virtue, wouldn't you say exactly the same thing?
Or, if you had a list like "dragons are immortals", "magical cats are mortals", wouldn't this be a lot worse?
No, I think there is a meaningful difference between the default being mortal with virtues for unaging and the default being immortal with flaws for aging. Certainly either way the storyguide can make it work out to the same net effect.
Or do you mean: Won't some people prefer it to be the other way no matter which way it is? Doubtless. There's no perfect world. But I do think...and this is just an impression, not a 'fact'.... that the mortal with Unaging option is more similar to how it has been.
As far as lists, something itemized at the level you mention would be pretty silly. IMS, the general rule is going to be something along the lines of "all spirits are immortal, as are most creatures with a Might >30; other creatures will have Ages Quickly/Susceptible to Deprivation by default. Unique individuals can be the exception, as always."