Do Animae Magic spells have a duration like other spells? That is, are the fae that show up bound for the duration of the spell, or do they show up, and the caster bargain for their services then and there, and persist until the service is done?
I'm assuming the muto versions do have a duration, but what about the Creo versions?
Also, are their base levels from Personal, Momentary, and Individual like other spells, or are they different...?
Steve
Yes, just like other spells, with base levels at Per, Mom, Ind. If you Creo Animal a wolf, it lasts for the duration of the spell and then vanishes. If you Creo Animal a faerie wolf, it's the same idea. If you cast the Creo version as a Ritual with a Mom Duration, it is permanent. The target is not compelled to serve you, though a Rego component would probably allow you to control it for the spell's duration. It's probably easier to bargain with it, though, since many faeries are willing to trade their services for very little, comparatively.
I'll perform some thread-omancy and use an existing thread for something related...
Are the various steps of the Becoming Mystery a constant, powerful mystical effect, like a longevity ritual, or more like one of the Creo rituals that bump an ability score up, where you'd get the warping for having the spell cast on you, and nothing else? The description leads me to believe it's more like the latter, not the former... Or is it something completely different?
Steve
I'd say that they are something completly different. But they are more akin to the creo rituals then they are to continuous duration effects.
I agree.
These are supposed to change your nature completely, transforming you into something else altogether, which becomes your new self. As such, they shouldn't incur warping, no more than any other immortality method.
Thanks for your answers, you've saved me some un-necessary rework. 
Steve
You've already gotten good answers, but just to back them up, I hadn't intended the Becoming rituals to be a constant source of Warping. The comparison to Creo rituals is apt. Another good analogy is the ritual of binding a familiar. Also, remember that once the Becoming is completed, the character doesn't have to worry about Warping any more, because it has a Might Score.
More thread-o-mancy...
This time a couple of questions, one about the about The Merinita cult itself...
How jealously do they guard their secrets? What kind of sanction could a magus face for sharing those secrets? If you've been reading along with Lough Caillte, you should have an idea what's going on. If not, I'll summarize : A well meaning bonisagus decides to help a somewhat addled (due to a Becoming Ritual that went astray) merinita maga, who willing agrees to the help, and teaches him what he needs to know. The ritual the bonisagus comes up with after years of work goes horribly wrong, and >pouf!<, he disappears. Notified of his demise, Durenmar is sending a magus to copy his lab notes for the Library there....
What could be some of the consequences the maga would face?
And the other... Is there anything in the Code that would allow a Magus who isn't very combat effective to appoint a champion if a wizard's war is declared against them?
Steve
(IC- we signed up for what???!!!)
OOC-
I would think that most Mysteries are kept fairly close to the vest, and probably some sort of Oath is involved in learning them. If nothing else, the mage that teaches such would become known as completely untrustworthy, if not ousted from the House entirely.
As for Wars, I would think that it's personal- it's not like naming a "champion" would then allow the original target to sit on the sidelines with complete immunity, but it then becomes a multi-war, one side vs another, but still to the death for all concerned. Essentially, one side declares WW against a target, and then "the Champion" declares WW against that first side - the original target is still in play. Certainly not a situation to be desired by the Powers That Be, but if the "champion" feels strongly enough to do so, well, no one is to stop them- it's war, after all, and no one should be kidding themselves about the stakes involved.
(As a side note, if enough magi felt strongly enough to get involved on both sides, those Powers might step in and negotiate some sort of truce or settlement/official judgement, rather than risk a major loss on both sides.)
Jealously enough-- it isn't a mystery if anyone can go learn it. I suspect the first thing that would happen when the Merinitae realize a non-Merinita has been initiated into some of their mysteries is for the non-Merinita to be offered a formal invitation to the House. Problems, if any, would arise if this is refused. On the lightest end, they might just treat the magus as if he were part of the House, no matter how stridently he might protest that he isn't. (Those who know Merinita secrets are Merinita, they might say, simple as that.) As far as punishing those who share the secrets with outsiders, they can refuse to initiate either of them any further into the mysteries until the outsider joins the cult, as a moderate penalty. At the most extreme, they can kick the offender out of the House. They probably can't charge them with breaking the code (although isn't there something about sharing mysteries as depriving the cult of their magic? I can't remember offhand), but they could always declare Wizard's War.
Wow, two horrible accidents. One might think the gods are displeased... perhaps some things outsiders are not meant to know? 
The Merinitae might argue that he's not Bonisagus any more, because he was initiated into their secrets, but that's weak and I don't think it would stand up at Tribunal unless there's something that says the magus agreed to it. Though it might be enough of a pretense for the covenant to forbid the Durenmar folks from copying his notes, at least until the issue is settled. Might this be a good opportunity for certamen? Challenge them for the right to copy his lab notes, if it gets to that point?
There's quite a lot that would have to be done to initiate a non-Merinita into Becoming. The magus would need to have initiated Faerie Magic first. Also, he's probably going to need to know at least some House Merinita Lore, and he'd need at least a score of 1 in Faerie Magic to perform the ritual (otherwise his Lab Total would be 0). After all this, I would imagine it would be perceived as either remarkable stupidity or an outright betrayal for a Merinita to initiate a Bonisagus into the cult's secrets without his agreeing to change his House, considering that Bonisagi swear to share what they learn.
She might be kicked out of Merinita, as I suggested above, but that's probably a last resort, because then there wouldn't be anything keeping her from sharing her knowledge with everyone. Wizard's War would be more likely. However, I would suggest they first pressure her to destroy the Bonisagus's lab notes. Another regrettable accident would remove the problem entirely. If she balks at that, they might have to destroy them for her, and then punish her later for her failure in other ways, like not teaching her any more secrets. If she already knows Becoming, though, she may not care. Might be better to simply wipe their hands of her.
Nope. Wizard's War simply removes the declarer and his target from the Code's protection against each other for the duration. A magus who isn't very combat effective needs to do everything he can to appease magi who take offense to him before it comes to war, because once it gets to that point there's not much else he can do.
I agree here, except that the not-combat-worthy magus can seek protection of another magus for the duration of the wizard's war, living in his sanctum. There always the hiding way or talking your friends into declaring wizards war against the agressor too.
As for them merinita and keeping their mysteries, especially the arcadian ones, secret according to HoH:mystery cults Quendalon taught them to mages outside his house when he returned in return for them joining the house and swearing an oath to follow him. Also it says his followers sometimes initiate members of other houses, particuarly Bonisagus.
From what I've read in HoH:Mystery cults and TMRE the Mystery cult houses are much more open secrets and are far less worried about most of their abilities being learned by others than the smaller mystery cults described in TMRE (with the exception of Verditius who want to keep their control of item creation).
Wonderful answers all. I can't say what in particular will happen, but it won't involve my players being at weirdness ground zero. Several suggestions I find intriguing, and will think about them.
Steve