It really depends on how much you have and where you want to end up being at. If you reach the level you want to be at, lets say $1/$2 for cash, then withdraw when you get a good chunk over 100bbs or whatever amount you want to play at. I really dont think withdrawing should affect how you play and what stakes you play at. I dont think there should be a specific time of when you withdraw unless you're a consistant winner. It should all depend on the stakes you're playing at and withdraw the excess you don't really need.