What is the average life of sperm after ejaculation outside the body?

Sperm exposed to the air on items like clothing, bed linens or toilet seats lose mobility (the ability to swim) rapidly. Once semen dries out, the sperm die.

That said, males should take basic caution after sex to ensure that any semen that may have come about from ejaculation is cleaned up (wash hands!) so as not to have any "unintended consequences".