How to tell when it is time to turn off the lights and go to bed already

Because sometime after midnight, people start getting silly and conversations go like this:

SAMUEL: I'm dead. I'm in purgatory, so you guys have to give me a penance.

ME: So you can get out of purgatory and go to heaven?

SAMUEL: Yes.

SHAWN: Hmm, well, you could skip lunch tomorrow.

SAMUEL: Skip lunch? But I'll DIE.

ME: I thought you were already dead. You're in purgatory, remember?

SAMUEL: Oh. Right.