No, I've banded as early as 3 weeks with no problems and had intact bucks get urinary calculi. The banding thing is a theory, nothing more. And yeah, once the band has been on for about 3 minutes, just leave it. Anything you do from there until they fall off is more harm than good.
If he's already banded, then it's too late to worry about it.
It takes as long as it takes, usually about 2 weeks
Do NOT cut them off! There is no reason to touch them, so DON'T TOUCH.