Until they go KA-BOOM! Just kidding...
Seriously... depends. With 9mm you can feel the brass getting softer when priming and going through the press. Usually I reload them about 5 times until they go through too easy or the primers go in too easy. Then for the last firing, I make my match ammo out of them so i can just leave them and sweep them into the corner/bucket.
45's can last almost forever. I have seen some old brass that you can't even read the head stamp any more. I know people still using brass they can't even remember how many years ago they were new.
357M and 38's usually split at the case mouth from the roll crimping before they get too old. I guess you can keep using the .357's by trimming them down to .38 length. That would eliminate the small split at the mouth but that's too much hassle.