How long can you stay up before you can't function?

Idk, I didn't try in a very long time but I believe at 24 I start having microsleeps. Around 21 I might start being dizzy and shaky. It depends on a lot how engaged I am. It's different to walk around the city, working on a project alone or sitting somewhere and having a really interesting conversation.

Two days is the maximum I go without any sleep/nap.

I can function after two days, but not do medical work in an emergency context. It requires in depth evaluation and analysis skills and hyperfocus. Being able to function and being efficient can be two different things.

I can't do all nighters like when I was young.

At 1 or 2 AM you start feeling sick.

If i need to be up unusually early, some solid rest is required beforehand.

Probably about 4 hours these days.

I caught myself passing out at the computer yesterday and had to go for a nap.

Around 11pm these days and I assume u mean for fun rather than "because of work."

I recently pulled an all-nighter working on a project. I was up at 8 am last Wednesday, then finally went to bed at 2 am that Friday morning. 🛌

Why, how are you working such hours?

At 26 hours I am feeling sick and can barely keep my eyes open.