Hey LuckyBetty,

A derm once told me that if a skin care product doesn't have an expiration date on it to follow, then to toss any eye cream or moisturizer where the water has separated from the product and is resting on top -- as this is a sign of a spoiled product.

For makeup I have heard to throw out mascara after three months of use.

For liquid makeup products (the most prone to bacteria growth) I have heard about six months, but that's depending on if you are cleaning your brushes properly and/or hands when applying. 

Better to be safe than sorry. 

Thanks for the tips Anna. I've basically heard the same thing as you,though I probably tend to keep things longer than I should.  I know if you use more organic based products that don't have preservatives, they definitely don't last as long.

I do think the way you touch your product makes a difference as well.  I.E. I with eye shadows, I never use my fingers on those products so I would imagine those would be less prone to bacteria than a lipstick and swap on multiple times a day.

These are just might thoughts though. We'll have to ask the experts on this one.

Thank you very much for your response and helpful information, Anna & Tracy! What do you think about perfume? How long does average perfume last once opened?

If I really want to know I contact the maker of the product and they always give me an answer.