guest service is open 24/7 so remove/change the DSC when you wish, if you’re off the ship for the majority of port time then you’ll likely always encounter long lines as everyone will be on board, as others have said no hoops to go through just a form they will fill out and you’ll sign to confirm, the reduction/removal will appear on your account normally the following day
tipping is a touchy subject on this board and some posters will take a instant dislike to anyone who mentions altering the DSC