How long does a man remain virile?

Answer 1

Until death. A man can father children at any age; the classical guitarist Andres Segovia fathered a child at age 92.

You can become sterile by having a vasectomy; some drugs have a side effect of sterility.

For women, their fertility peaks between ages 17 and 24, after which it declines. Female fertility begins to decrease rapidly after age 33 or so.