from about.com article:
Concealer Up to 12 months.
Powder 2 years.
Cream & gel cleansers 1 year.
Pencil eye liner Should be sharpened regularly. Will last up to 3 years.
Eyeshadow Will also last up to 3 years. Extra tip: A dark eyeshadow can double as eyeliner, in fact, most makeup artists swear by eyeshadow used as eyeliner. You'll need a super-flat eyeliner brush for this (MAC, Sephora and Aveda have great brushes). Get the brush a little damp and dab in dark eyeshadow (black, brown or deep jewel-tones work great). Wiggle the brush into your lash line focusing on the space between your lashes, then sweep the color just above your lash line.
Brushes Wash every 2-3 months in a mild detergent.
Sponges Wash weekly and discard monthly.
Foundation Check the ingredients: A water-based foundation will last up to 12 months, oil-based will last up to 18 months. You may find you need two different shades of foundation each year: One for summer when your skin is naturally darker and one for winter when you're lighter. Extra tip: If your water-based foundation dries out before it's expiration date, simply add a few drops of alcohol-free toner and shake to mix it in. No need to do this to oil-based foundations. Because they contain oil, they will tend to separate. You have to shake anyway.
Lip liner Up to 3 years. Extra tip: Skip the push-up lipliners. They're expensive, tend to break and you never really know how much you have left until you run out. No need to spend money on lip liners, there's no secret to greatness for this product. Save your money for powders and foundation.
Lipstick Some experts say 1-2 years. Others say up to 4 years. What everyone agrees on is that if it smells rancid, throw it out, it's spoiled. Extra tip: If you store lipstick in the refrigerator, it will last longer. Bonus tip: Want your lipstick to last longer during the day? Shade in lips with lip liner before applying lipstick.
Mascara This product expires the fastest: Throw out after 4 months. Extra tip: If you don't want your mascara to expire faster than its fresh date, don't pump the wand in and out -- you're only exposing the product to drying air.
Nail Polish Up to 12 months, depending on the quality and how many times you take it on a plane (the cap always unscrews on me during flights, leaving my purse a -- fume-y -mess)