[Jim T]

When you first come in, you either pay a big blind to play the first hand, or you wait for the blinds to come around to you.

If you leave, when the blinds come around to your spot, they put a token at your place to help the dealer remember (or a new dealer if they switch) that you have to pay a blind again when you come back.

You don't gain any advantage by leaving in between hands in Hold em, believe me. I don't know how they handle Stud though. I didn't play it when I was in Vegas.