In thinking about it a bit more, what I think I'd do is, instead of having a maga do this, is to instead allow the Diviner to add their Int+Divination ability to any Aging roll - to represent them using their Divination to make life generally better for themselves.
It's the in-game version of "if you're a prophet, why don't you predict lottery numbers?" Well, with Divination, you might not be able to do that - but you can make life a lot easier for yourself, just in general.
I understand the view you're proposing but still can't bring myself to like the application of HD to aging. To be fair, I think of it to be closer to a magic eight ball result than a yes no; in spite of what the rules say. 
Hermetic Divination can only tell you what is true NOW, it cannot break the Limit of Time. A Quaesitor that suspects you, or that plans to visit a village where you've interfered, those things will follow an obvious course.
Anything that is accidental, such as twisting your ankle or that Quaesitor passing by at the wrong time, is outside its scope. And that include any and all issues that are resolved by rolling a dice.
Looks very arbitrary to me.
To avoid impacts on campaigns you wish to join, better leave be. Especially considering So, Uh, Playing Ars by Yourself These Days
Cheers
Fair 'nuff.
...OK, that came out of left field. And requires quite a few assumptions regarding a number of things about people you don't know, and scenarios you weren't involved in, and even my reasoning for posting this question, that I'm not particularly interested in clarifying on an internet forum.
And the fact that you didn't realize this means you're not someone I care to talk to for the time being.
Goodbye.
I don't make assumptions about your campaigns.
I just answered your
with a recommendation, in the light of another post of yours.
Cheers
Anyway. Moving on...
That is certainly a good point.
That is also a good point - however, is that a rules interpretation, or RAW?
That's not what's being discussed. I fully concede that the roll occurs during the winter, but that represents a number of injuries that occur during the year - and that as a consequence, having the LR in effect only during the winter wouldn't be effective.
That's one theory. The other theory is that aging occurs quickly, as a consequence of injuries, and an older body's inability to heal as effectively. Or it's both. That's one of the issues being discussed. The question here is what occurs if a Longevity Ritual is engaged only during times during which that kind of aging occurs - usually on adventures, but also potentially during times that a regular predictions for your health suggest that such an injury may occur.
My theory was that Hermetic Divination, if done regularly, might be able to predict such activities. "Will I be injured today?" - if so, turn the LR on. If an injury occurs, leave it on until the injury heals. If not, leave it off.
Alternately, the Hermetic Divination, if done daily, may also indicate that your body will "naturally" decay every day enough that it's functionally up most of the year - meaning that you'd take warp normally.
My original question was "well, OK - what would that look like over the course of a year" - and I came up with "doing the aging roll beforehand, and figuring out if the PC needed to have the bonus from the LR to protect him. If he needed it, then it would be up. If not, then it would be suppressed."
Rego Vim can suppress an enchantment or ritual magic just fine - Aegis affects them, after all - as does Guttering of the Hearthfires. Perdo Vim affects completely non-Hermetic magic just fine as well.
EDIT - and enchantments cause warp through their effects, not through their existence; otherwise, simply wearing an enchanted ring would cause warp (which it doesn't.) And effects are treated just like magical effects. Rather, I would argue that a LR matches a Watching Ward (with its single use, indeterminate ending) with a delayed CrCo healing ritual in it, more than anything else. And Vim can affect those just fine.
So the suppression effect, to me, is fully within RAW - you just need to design a specific effect to do it. Regarding whether a suppression effect itself would cause warp - as stated in the Vim section, Vim spells can target either effects, or individuals (creator's choice). Therefore, it seems that you're arguing that someone who is not the target of the suppression effect can take warp from the spell - which runs counter to the description of long-term warping.
If that were true, then the LR would not provide a continuous bonus to resist the effects of aging. What you are describing ("a delayed CrCo healing ritual") is just one of the components of the LR -- the one that makes sure that the magus does not suffer from the negative effects of an aging crisis.
I disagree that it is that clear. The longevity ritual is something that is much more powerful and integrated into the magus' being. It is not simply an effect that is applied to the magus (such as a simple Purification of the Festering Wounds would be). It is also quite personalized to every single individual. And since it is the result of a seasonal activity that requires raw vis, I would consider it unbalancing if a simple spell was able to suppress or dispel it. At a minimum, it should require a ritual (much like Disenchant).
Very much a YSMV topic. Certainly not clear-cut RAW, IMHO.
Trying to mechanize "cannot scry" from Limit of Time, using the last column on p58 of TMRE. I would say "rolling a dice" is a pretty good match, although having 10% or less of failing might be considered "should succeed" for Divination purpose.
Just to add some fuel to the "suppressibility of the Longevity Ritual" side of the discussion, I'd point to RoP:F, p.129, the first of the Ware guidelines:
In looking at the guidelines list, we've also got the following under Perdo Vim (emphasis added):
Which seems to be a generalized version of Disenchant, in the PeVi section of the main book. So this tells us that a Longevity Ritual is considered to be a type of enchantment. OK. I fully agree that DISENCHANTING an enchantment is a ritual. However, In looking at the Rego Vim section, I'm not seeing any requirement that SUPRESSING an Enchantment is a ritual. We do see examples of how to suppress a Ritual (again - Guttering of the Hearthfires), which is considered to simply be a normal spell. I'll look a bit more, but I'm not finding anything (again, serf's parma) - but that tentatively tells me that either
Of those two options, #2 seems more reasonable.
To explicitly state my reasoning:
My advice is to be really careful with this. If ReVi can suppress a Longevity Ritual this easily, then a foreign Aegis of the Hearth should as well.
That was my initial thought as well. It also came up in my research for looking for justifications for suppression not causing warp - but then the long-term warping rules specifically call out wards as causing warp for individuals inside them (even if they're not part of the Form of the ward), with Aegis and Parma being the explicit exceptions. Hence my focus on individual spell targets for suppression, rather than targeting the individual human being. But then I realized:
My main thought was "only if you're in someone else's Covenant without being given a Token for 3 seasons - probably if you're copying a text, or something like that." Other than that...I couldn't think of anything (other than being held captive) that would qualify.
It's amazing the kinds of problems that pop up with Aegis of the Hearth. What about Familiar Bonds? I hope if 6th edition ever shows that Magic Resistance in general operates in a consistent fashion (easiest solution is probably to make all spells Aimed and give everything with MR a bonus to defense).
I believe it's been established that Familiars count as magical creatures, so unless they are given Tokens, they are affected by the wards like anyone else. (ie, they can't enter unless their MM is higher than the Aegis, etc.)
I would imagine that the Familiar bond is considered to be an enchantment with a magnitude of whatever the total the magi used to create it. If it's not high enough...it gest surpressed.
However, I seem to recall that there was an exception for effects that were already running - ie, if it's already been cast, Aegis doesn't affect it. If that were the case, then Familiar bonds and LR's are safe.
Of course, I could also be smoking crack on that.
Hmm, I remember something about losing (or not) invisibility when entering the Aegis, but not where the discussion ended.
Well, just looked up the Aegis, in the book (AM, pg 161). Looks like Aegis specifically DOES surpress effects that are cast outside it, but brought inside:
Further,
As to whether it affects a LR or a Familiar Bond? Doesn't specifically say. However - they are magical effects, and they are defined as Enchantments. So I would argue yes. However, the RAW text only calls out "enchanted devices" - which in AM5th specifically refers to only Talismans, Enchanted devices, lesser enchanted devices, and one-shot items.
As such, I think that while the case can pretty strongly be made that both LR's and Familiar bonds are affected by a hostile Aegis, it's not specifically mentioned in RAW.
However, I'd still argue that they're affected. The consequences of that, however, don't seem to be very important, as it's only affected by the "1/2 the level of the Aegis" aura effect. And what's the minimum level of a LR? I'm guessing at least 25 for most magi, if not 30. So they'd have to be hanging around in a hostile lvl 50 Aegis for 2 seasons a year for it to be an issue. Similar with the Familiar Bond - it would be suppressed at 1/2 value, so the magi would have to have a bond of similar weakness (25 or so) in order for it to affect them.
However, neither a LR nor a familiar bond has penetration - so it may very well be that their penetration is (0), at which case it's automatically suppressed. If that were the case...I can certainly see an issue with not spending a lot of time in a hostile Aegis - but mainly for the familiar aspect: if I had one, I wouldn't want to be cut off from it. In contrast, the (lack of) issue regarding the LR still stands: unless you plan on being there for a good portion of the year, it's a trivial disadvantage.
Careful, you've included a really big assumption that hasn't been written into the rules. Consider a being with Magic Might inside the Aegis of the Hearth. It tries to use a R: Personal power with 0 penetration on itself. The effect is resisted, yes. However, that means the penetration is reduced. This means... it still works because there is no resistance. (Negative penetration is OK if it doesn't need to beat Magic Resistance.)
The issue is that it doesn't say how items are resisted, just that they're resisted. Meanwhile there are different ways of dealing with resistance (spells vs. powers). See here for more information: A Guide to Aegis of the Hearth
This is why I only warned caution. Aegis of the Hearth is not necessarily an issue alongside ReVi suppression. It depends on how you play the Aegis.
So,
The way I would rule it is that circumstances change.
If the Divination suggested that no debilitation would occur for the year, and the magus then suppressed the LR, I'd rule that cirumstances changed dramatically when I "surprised" the player with a reroll without benefit of the LR.
Similarly for the opposite.
This isn't really screwing the player; using divination to avoid destiny never works out well.
Anyway,
Ken