So, the base cost of a familiar is based on their size: 25 + (size*5). OK, fine - but what if you've got a baby familiar that will grow in size over the next few years? Do you pay for the maximum size, or do you pay for the size they are at the moment of the ritual (and then stunt their growth somehow until you do the ritual again)? Or do you do something in the middle, whereby you "bank" some of your lab total for part of their growth, and then re-do the ritual when they reach that size (and hopefully by then, you've increased your lab total enough taht you can redo the ritual)?
I'm asking because my ReVi ward specialist managed to get ahold of a baby dragon - currently size -1, but will be size 8 in a few centuries. Needless to say, this is a non-trivial amount. Sure, he's got a lab total of 75, so he can handle it - but it will kinda suck if he has to spend 65 of it to cover the size, when he won't be able to take advantage of that until after he's dead, because the character won't live for more than 100+ or so years. (Mainly the character is looking for the botch dice reduction, plus the cool factor.)
Alternately, I suppose the famiar ritual would boost their growth, just like it boost their intelligence...but this implies that we'll end up with a highly-intelligent, inquisitive, juvenile dragon in an ancient dragon's body within a few seasons. Which I suppose might be [strike]horrifying[/strike] amusing.
EDIT - It's kind of like Clifford the Big Red Dog, only medieval, and with more running and shouting and setting things on fire.
Mainly I'm looking for some general guidence, here.
I'd say you can start out lower and just add refuel it if you current alotted room is filled, but take a risk of the bonds breaking if you don't add bonds soon enough.
Remember that a magus binding total is not divided between points to bind and points for cords/powers.
If your lab total is 75, then you have 75 points to spend on cords/powers regardless of the size (or Might) of your familiar.
So in your case, it's a fairly moot point to worry about what's going to happen as it grows, because that can be handled by the current lab total.
The problem is interesting of itself, though.
Personally, I'd say that once you bind a familiar, it's bound, even if it grows later to tremendous size and Might. It makes sense that binding a dragon while it's young should be easier, and that the bond should endure once formed. I think it's also technically the closest match to the RAW.
You could alternatively rule that later growth (in size or Might) shatters an "insufficient" bond. In that case, strengthening the bond before it becomes insufficient would probably be enough to prevent the shattering.
Great. I'd fetched my core book, constructed an argument and sat back down to explain - and then ezze has it all exactly right already.
All I can really add is:
if this was not the case, everyone (well, many at least) would bind magical mice (or other, similar sized critters), simply because the size -10 would provide such a bonus for cords. So I'm rather happy minimum bond strength is not subtracted.
Heh - I figured this was the exact reason for why most "classic" familiars were toads, snakes, and mice - that folks mostly went with the larger animals only if there was some sort of physical capability the animal had that wasn't found in the smaller creatures (plus, concealability). So I guess the real reason is that wizards are cheap bastiches when it come to vim use.
