re: How long after closing is it rude to stay at a restaurant bar or table?

If it's time to go you'll hear it directly or inderectly, through body language, etc.

Obviously with accepted late seating it's an asummed trade off for your additional service

If it's not acceptable they still want you back and will let it slide

Too many factors and wether they are pushovers or not

I think you're thinking about it too hard. The model saint leaves by closing, a lot of people will do what they can get away with. Stay late with them moaning and groaning then not tipping is a dick move

How well people treat people that they don't owe anything says a lot about them though