How long does pizza dough keep in the fridge?
As long as there's no mold in it your dough should be ok. Flavour and texture will start to degrade due to the yeast dying out (as you found already).

Technically, you'd get better results if you feed that dough regularly with more flour like a sourdough - which can last virtually forever!

Other than that you could also freeze the dough balls and just defrost a day before you use it. Frozen dough should last for months with no change in texture or flavor if there's no freezer burn.