Yeast
Well-wrapped and refrigerated dough will stay usable for a week, maybe ten days. Using slightly less yeast than the recipe calls for will give a higher proportion of yeast food to yeast beasties, and as a result, the dough will last longer in the fridge.
(You see, yeasties will multiply and do their special one-cell mambo until they run out of food, at which point they die. And once a critical mass of yeasties dies off, the rest of them do the lemming thing, and the process of die-off accelerates. That's when your dough starts to smell "funny"; it's yeast corpses. So, having a higher yeast food to yeast bodies ratio helps slow down/prolong/retard the yeastie-beasties' life cycle.)
In short, balls of the stuff in the fridge should be good for a week, easy.