Honestly, I never actually go to the front desk and check-out. I don't think it's required. Just remove the "Do Not Disturb" sign and leave.

At US properties, you can simply plant yourself into the lounge before 4pm. There likely won't be an attendant anyway since they only show up for hors d'oeuvre which usually doesn't start at 6pm. If you feel like it, you can ask for permission when the attendant does show up but I see no reason why he/she would refuse you. The only thing to keep in mind is that sometimes the key expires after regular checkout time and you have to go to front desk to have them re-key it for 4pm checkout.