Generally, 24 hours will do.
I spent the night at McDonald's for free. The waiter said nothing. The waiter is very good.
I don't know Just don't litter. The waiter works very hard. I saw that they would clean up after five o'clock that day. There are many people staying there for the night, and there is a lot of rubbish. Understand the waiter and don't litter.
By the way, please take care of your things. Everyone has it now.