OK, I realize that this is a fantasy universe, but even here, the Second Law of Thermodynamics has to apply. So Warlow's plan of just endlessly recycling blood between himself and Sookie is never going to work -- with each cycle, they're going to lose a little energy, because they need to use some just to live. (Un-live?) Ultimately they'll have to feed on someone else. Strange that Billith didn't already know that Jessica was gone / in trouble -- he had no trouble sensing Sookie's distress.