I've used previously purchased mugs at the WL. I am aware that they have signs now that they are for your current stay..but when we purchased our original mugs they TOLD us they were good forever. The logo and mug haven't changed. If it did..I'd probably buy new ones..just because I'd like to have them anyway. I personally don't loose sleep at night because I've re-used a mug from a previous trip. I've also seen people from the Caribbean Beach and POR fill their mugs at the WL. Now..I'm not saying that's right either..but no one has stopped them. We stay at the Lodge..but like to go to the food court at the Caribbean Beach..and no..I don't take my WL there. When we stay at FW I look forward to purchasing an official FW mug. In any case..I don't think the Disney Police jump out from behind the soda dispenser with lights and sirens, throw you to ground..cuff you, and in the name of Walt arrest you. Worst case scenario.. they'd probably, very politely ask you to purchase a new mug.