We gave our kids charging privileges after about our 2nd or third cruise when I had to stop what I was doing to go buy Jordan a hairbrush because she forgot to pack hers.
They both know that they're allowed "X" number of charges for the arcade and that they have to ask before buying anything in the shops...and it has worked. They're very good about it. Too bad I'M not!
Both were given sign-out when they reached the "legal" age, and we keep post-it notes on the inside of the door to the room so that we know (fairly well) where everyone is at any given time. I got a kick out of the concierge using our post-its to leave us notes!
Yes...we did have to have a conversation about misuse of the elevators, but after they saw a group of kids get in SERIOUS trouble (they "broke" an elevator and got stuck in it) they knew it could have been them in there, and haven't been a problem with that since then.
As for hanging in the stairwells.....the older mine have gotten, the more secret places they've found.....so we haven't caught them there. We tried to tell them that they were disturbing other passengers, but once they get with a whole crowd of kids, we lose a little of our authority. I'm sure that they were told more than once to scram.
Castaway Cay....as long as they each had a friend, we let them take off and do what they wanted (and Dad & I got to go to the Adult beach for the first time ever!) when the youngest turned 13.
Once or twice we ran into them somewhere along the way....and they knew when to meet us for the Banana Boats or whatever we'd planned...and they also knew what time they had to be back on the ship.
I guess we're too lenient, but so far it hasn't backfired on us.