Here we are once more. Today’s question is different from the others, though. It’s not about stars, their wives, nationalities or heights.

Let’s get to it, I don’t want to keep you hanging in suspense!

“how long could you live in a underground”?

I’m assuming here that there’s a word missing [bunker], because surviving in the subway, I don’t think that works too well [no water, no food]. And if it’s somebody wondering how long they could disappear for, to go live in the underground, the question is pretty much unanswerable. Some people do it till they die and are never found. And some people don’t manage at all.

Therefore, bunker it is.

I can only speak in the most general terms here, as I don’t have enough information (what kind of bunker, how many people, private or public, etc etc), but professionally built (military) bunkers are usually fit for very long survival. As long as there’s food and water, everything’s fine. They usually have their own air circulation, generators and medical facilities.

Thing is, usually there’s a reason that somebody goes into an underground bunker and that reason might find a way to get into the bunker or to get the people out.

So, if nobody goes mad, the food runs out or something/body gets in or out, who shouldn’t, they can sit there until the end of time.