The average bottle has a lifespan of about two years, says nail expert Tina Wang, owner of Lunula Salon in Brooklyn, New York. That being said, rather than being married to this hard and fast timetable, it's more important to consider how often it was used and how it was stored, she adds.

Nail Polish Opened bottles should be tossed after about two years. Unopened, they can last indefinitely, says Annette Soboleski, a nail technician for polish maker OPI. Once a bottle has been opened, some ingredients will evaporate, causing the polish to thicken and separate.

Composition of Komilfo gel polishes: Acrylates Copolymer, Isopropyl Alcohol, Butyl Acetate, Dimethicone, Microcrystalline Wax, Parfume, Mica ±: CI 15880, CI 77491, CI 77492, CI 77891, CI 77163, CI 77007, CI 77266.

There are two polymers commonly used: nitrocellulose and cellulose acetate butyrate (CAB). CAB is the polymer used in non-yellowing top coats. If the product contains nitrocellulose, you can be sure it is not non-yellowing.