Does nail polish evaporate

Bottles usually don't have an expiration date, but it does thicken with time. To keep it lasting longer store it in the fridge.

Try rubbing the nail-polish bottle in your hands (like trying to start a camp fire with a stick.. except just the bottle!) if the layers separate or become too "runny". If the nail polish becomes "chunky" try adding a drop or two of nail-polish remover and shake until smooth.