i have a bark eyeshadow from around 1997, and a savory lipstick from around 1998 and it doesnt even stink, though i dont ever use it anymore. i think with lipstick it just depends because i have had some for less than a year and they already smell bad. i have melody eyeshadow, ooh CCB, and frankly scarlet blush from around 2000 and they are all fine though sometimes with powder products they begin to develop a sort of hard film from not being used. i think you just have to go on a case by case basis and if the product smells funky or isnt of the same quality as you remember it, toss it out. I think mascara is one thing you shouldnt keep for a long time and second to that would be lipglass simply because of the moisture in it and the potential to build up bacteria.