Liquid/Cream Foundation - 1-2 years
Concealer - 2 years
Powder - 2 years
Mascara - 3-6 months
Liquid eye liner - 6 months
Lipstick/Lip&Eye Pencils - 12-18 Months
Lip gloss/balm - 8 months
Eyeshadow - 2 years
Powder Blush - 2 years
Cream Blush - 2 years
Eye Cream - 6 months
Moisturizer - 2 years
Sunscreen - 2 years
Face Cream - 2 years
Nail polish - 1-1 and a half years
This is just a guideline of course. Just remember, if it smells/looks funky or has a weird consistency...throw it out! If you're not sure, ask a beauty professional.
The best way to avoid feeling like you're wasting a lot of product is too only purchase makeup that you're going to wear more than once in a two year span. Don't purchase a $30 lilac blush simply because 'the color is soooo pretty!!!'. If you find that you're not wearing certain blushes or eye shadows, give them to a friend who'll appreciate and use them.
And remember, ladies! out with the old, and in with the new! Getting rid of your old makeup products, makes room for new makeup products! So, getting rid of your expired beauty items isn't a time to mourn, it's a time to whip out that credit card and shop shop shop till you drop!