If you prepare the bottle then stick it in the fridge, 24 hours. If LO has sucked on the bottle, you're supposed to use it within an hour. I don't exactly observe the 1h rule and have been known to put leftovers in the fridge for the next feeding if she leaves more than 2-3 oz. I just can't stand the waste.
Re: Dumb formula question
24 hours or so.