Takeuchi: Do the 11 stacks of God Hand recharge over time?

Nasu: Yes, since Illya's prana pool is absolutely ridiculous. If Berserker's Master was instead a mage of common power, they could spend their entire life generating prana and still fail to muster up enough to power even a single revive spell. For this reason, a less formidable master would mean Berserker would have to fight his way through the Holy Grail War with only 11 revivals. Of course, that's still plenty of lives by any standard. With a Master of Illya's caliber, though, Berserker is able to be revived 11 times in a single encounter. On top of that, once Berserker has been wounded by a specific attack, that same attack will not be effective a second time.

Fate/complete material II; Characters: Berserker, pg. 64-65