professor and major, can you expand on what you do? when you go back and forth are you rinsing the yeast and then creating a new starter everytime? to me, it sounds like the OP was just going to toss a batch on top of an existing yeast cake, i'm assuming you guys aren't doing that.
I normally just reuse part of the slurry (I pour the slurry in a mason jar and refrigerate) - washing is a PITA and I never saw any real benefit from doing that (of course, I leave most trub and hop material in the kettle). If the slurry is over a couple weeks old I usually make a starter on my stir plate or with continuous o2.
As far as the acetobacter goes, its your call richardt - keeping it cold will help keep the slurry fresh. But if you are like me, if you have even the slightest doubt of its health and/or purity you will dump it. If you feel good about it - use it!