I guess I'm too cheap, because I can't imagine not re-using my leaves as much as possible ... I spend way too much on tea to just throw them away after one steep!
Of course, I also tend to brew gong-fu or semi gong-fu, with more leaf than western-style brewing usually uses.
I would recommend that if you want to use more leaf and go with shorter brew times to get multiple steeps, that you should be able to keep your leaves at least overnight at room temperature. I've done it multiple times and never gotten sick. Or you can also put them in the refrigerator until you're ready to brew again (though I wouldn't do it for longer than a day, and I don't do that with yixing or other antique/precious teaware--I'm too paranoid the sudden temperature changes might cause them to crack).
This seems to work best with black tea and roasted oolongs--you can do it with greens, but it tends to lose its freshness, IMHO. I have one particular white tea that just lasts *forever* (8-9 steeps, easy) that I can do this with as well.