There are about 225-250 drops of oil in each 5 ml bottle of essential oil. In general, if stored in the amber bottles and not exposed to high heat, the oils can last at least 2 years or even longer. Citrus oils tend to not last as long as other oils. A few oils like Vetiver and Patchouli can actually improve with age. The lifespan depends on how often and how much is used, but the expiration dates depend on each essential oil – these are listed on each bottle.