(Normally I don't put my formspring answers up on my blog - instead they're usually up on my Twitter, Facebook, and of course my Formspring page, and I don't want to duplicate content too much. But I thought this question was interesting, so I just put it on my blog too, in case anyone else was wondering.)
I don't think it helps anything, because nail polish isn't like other cosmetics. Other cosmetics, especially creams or liquids, tend to go bad or go "off" after awhile because bacteria get into them and start multiplying there over time. This is why some people suggest putting some of your makeup in the fridge, because the cooler temperatures slow down bacterial activity (although it doesn't stop it complete, and it doesn't kill the bacteria inside). However, nail polish is different. The chemical composition of nail polish is such that it's a very unfriendly place for bacteria to live - in general, they just don't survive in the sea of chemicals found in our polish. So nail polish has very little bacteria compared to other cosmetics. So since there isn't much bacteria surviving in your nail polish, there really isn't any point putting it in the fridge, because nail polish doesn't go bad the way other cosmetics do. However, over long periods of time, the solvents in the polish will evaporate naturally, and the polish will thicken or dry up. This can be fixed by adding thinner to the polish. (A side note - it's thinner you want to add, NOT nail polish remover, which will mess up your polish!) I hope this helps you!
