Sperm outside of the body can live for around 20 minutes to an hour. The rule of thumb is to avoid contact with semen (or other bodily fluids) while they are still wet to avoid live sperm or bacteria. If the semen has dried, been wiped off, or washed off, there are no longer any living sperm.
In certain environments such as the female reproductive tract beyond the cervix, sperm can live for as much as five to seven days. The woman’s cervical mucus gives this long life to the sperm. In other biological environments such as the vagina, sperm may live only a few hours. In contrast, the egg has a life-span of only about one day from the time it bursts from the ovary. Thus, fertilization can occur anytime live sperm meet up with a live egg, which can happen even if the sperm are deposited up to seven days in advance of ovulation.