Outside of the body, sperm may die quickly when they're exposed to the air. The length of time they stay alive has a lot to do with environmental.
It often does, of course, but most sperm die before making it to their final Sperm needs moisture and warmth to live, so once exposed to air.
On a dry surface, such as clothing or bedding, sperm are dead by the time the semen has dried. In water, such as a warm bath or hot tub, they'll likely live longer .