Do you have some mascara from last year? How about some eyeliner that is from 2008? Here are some guidelines for how long you should keep your make up products:
Lipgloss - 2 to 3 months
Lipstick - Up to 1 year
Mascara - 2 months
Eyeliner / pencil - Up to 1 year
Foundation:
Water based - 6 months
Oil based - 1 year to 18 months
Brushes - Wash them every 2 to 3 months