Lots of info on this with some varying details. Generally speaking your starter should be finished by 24-36 hours from when you pitch. If you are crashing and decanting, 24 hours in the fridge should be good. If I am brewing on Saturday, I'll make my starter on Monday or Tuesday at the latest. If crashing, it can sit in the fridge for a few days with no issues. This is what I generally do with great results.