Here's a very interesting article on how long you ought to keep
your beauty products for!
Ladies, pay heed! 
"From eye shadow you bought last year to the minty lotion you got
two birthdays ago, your vanity is likely to be full of items you
think are too nice to throw away but that you rarely use.
While some cosmetics last up to three years, others - like that eye
shadow or mascara - must be replaced every few months.
"Preparations can break down, making them less effective and
putting them at greater risk of contamination," says Irwin
Palefsky, Snr Vice President of Cosmetech Labaoratories, a
consulting firm that develops products for beauty companies.
Even though most cosmetics contain protective preservatives, it's
important to know how ingredients affect such products. Those high
in water content provide a breeding ground for microorganisms.
Preservative-free products are easily containated (as is eye
makeup, which has limited preservatives). And items containing lots
of oil can go rancid if exposed to air often.
To keep track of beauty products, label each with the date of
purchase or receipt. Then go through your supplies every couple of
months, and do a look, feel and smell test. Does it look cloudy?
Has the colour or texture changed? Is it bulging at the lid? Is it
separating or difficult to spread? Does it have a strange smell?
Let the answers, and the timeline and tips in the chart that
follows, guide you.
From : Martha Stewart's Living, 2002?
Written by : Patricia J O'Conner
The chart follows... 
