It depends. Lack of air circulation can cause problems in minutes as people can end up breathing stagnant air. Less of a problem if you have artificial gravity as then you have convection and/or the coriolis effect to help keep the air moving. As for actually running out: less of an issue.
I recently saw a DS9 episode where O’Brien said life support is down and it’s going to be a problem in a day or sth, was pleasantly surprised at that.
Might still not be accurate, but at least it was not a “oh shit we’ll die now” kind of thing.
It depends. Lack of air circulation can cause problems in minutes as people can end up breathing stagnant air. Less of a problem if you have artificial gravity as then you have convection and/or the coriolis effect to help keep the air moving. As for actually running out: less of an issue.