Suntan lotion can last for up to three years. However, some products have a specific expiration date or a date when they are no longer effective.
Suntan lotion that has passed its expiration date should be discarded. If sunscreen is used liberally and regularly, it is unlikely that there will be any expired product leftover the following year. An ideal amount of application for the entire body is about one ounce, or enough to fill up a shot glass. The American Academy of Dermatology recommends wearing a sunscreen that has an SPF of at least 30. The product should be applied 20 to 30 minutes before going outside.