I will note that the system has an existing hack. As long as one of these magical girls has a continuing supply of grief seeds to use, and the will to use them, they can keep going indefinitely. All you really need to do is have someone reverse-engineer the grief seeds and figure out how to produce the dumping-off effect without requiring witches to eat people in the process.
Personally, I note a *really* entertaining idea for this. At one point, QB said that he ate used grief seeds because if he didn't, and they kept being used, that could resurrect the witch. Presumably, then, witches can somehow run off of corruption. If you could just bleed off the corruption, then, and use it as the powersource it is... well, it would be interesting to figure out what sort of a thing would take corruption energy and turn it into something useful, but I can't really see Raven being opposed to the whole "warping dark side powers to good uses" schtick.
Personally, I note a *really* entertaining idea for this. At one point, QB said that he ate used grief seeds because if he didn't, and they kept being used, that could resurrect the witch. Presumably, then, witches can somehow run off of corruption. If you could just bleed off the corruption, then, and use it as the powersource it is... well, it would be interesting to figure out what sort of a thing would take corruption energy and turn it into something useful, but I can't really see Raven being opposed to the whole "warping dark side powers to good uses" schtick.