ONE. There's no answer to this. Obviously it's best to get it done in 1 shot. It's like asking how many times can I repeat a course before it starts to look bad. Well, if you take organic chem 3 times and fail it, I think dental schools are gonna get the message that you suck at organic chem.
BUT....it's better to apply with a good DAT after 3 attempts than a bad one after 2 attempts. You just have to decide if your DAT is bad enough to take it a third time.