I read a post a while back from Danger Dave. It might of been on his Dragon Blood thread, I'm not sure. He fermented a 20 gallon batch of wine with 1 packet of yeast. It was kind of an experiment, and he was ready to add more but he didn't have to. The yeast multiplied to a sufficient level to ferment the entire batch. I'm not endorsing that kind of trial, just stating what he had said.