Yes, they do expire! An average lifespan of a nail paint bottle is 24months, after which it becomes lacy. Some of you keep the bottle hydrated by adding nail polish remover if you find it expiring. The outside climate also influences the lifespan. Too much humid, cold, or hot atmosphere twist the chemical formation inside the bottle and make it expire soon. If you live in such extreme temperatures, you would be better be with small portions. So, buy small bottles so you can finish them before it gets worse. Or even if you are not someone who wears nail polish daily, you can buy small portions.