Oh, whoops. I had originally intended to add a skill that allowed you to release souls, but I completely forgot it. I'll fix that.

Exhausted souls automatically recover eight hours after they become exhausted, whether the Soul Keeper rests or not.

I don't know whether not having to sleep at all is too great a boon for Soul Keeper anyway, since even if they could use all their abilities continuously, the vast majority of the damage they do wouldn't stack with what their allies are doing (unless said allies are sneak attacking with saps regularly or taking -4 penalties on their attack rolls, I suppose?)