[aeni]

Until your shadows turn color or start to smell, you should be ok. One of my instructors has some very old MAC shadows (when the packaging for the shadows was larger and had way more product) and they're still good! Those powders are meant to stick around. Anything liquid or creamy is meant to be used up within a certain amount of time (foundation, mascara, liner, lipstick, etc - though I've found that using alcohol to clean liners and lipsticks help in the long run).