I don't know, until they're goopy? but even then, I've heard you can revive them with a drop or two of remover. I dont' know if there's a specific time limit
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Fashion is art you live your life in. - Devil Wears Prada | formerly ttara123
I don't know, but when I was a kid my mom kept the nail polish in the fridge because she said it lasted longer that way. We kept it in the door where the butter tray would go.
I think it depends on the brand. Some of my Revlon stuff has been in my drawer since mid college (I graduated in 2000) and I can still use it. I had some VS nailpolish that separated to the point where no amount of shaking it would fix it, and I threw it out. Most of my Revlon stuff keeps well for a few years. I store it in a drawer, so maybe the darkness helps preserve it. I've never heard of the fridge thing... I might try it and freak my husband out.