When do AMC theaters close their concession stands?

Yes, it might be closed by the time the movie ends

I work at a theater and we tend to start closing down concessions about a half-hour before the last show goes in (cleaning up things like the deep-fryers, pretzel-ovens, etc.) and we officially close about 15 minutes after the last scheduled showtime. It could be different for other theaters, but I work at a big chain, and it's just not worth it to keep the concession stand open any later. Very few people tend to buy concessions at the later showtimes and it's just a waste of money and time to keep the stand open and staff on clock to help maybe one or two people who might come out after the final showtime begins. If you want a refill, just see if they can fill up a courtesy tray or box when you initially buy your concessions and count that as your refill. That's what we usually do.