A man goes to visit his doctor and tells him:

"Doc - when I was twenty I would get an erection and it was hard as a rock and as stiff as a telephone poll. When I turned fourty I could bend it a little. And when I turned sixty I could bend it in half".

"So what do you want to know ?" the doctor asked.

The man replied - "Good Heavens Doctor - how strong will I be when I turn eighty ?"