How strong?

An old man goes to the doctor to ask him an important question.

"Doctor, when I was in my 20's, it took both of my hands to push down my hard-on."

"When I was in my 30's, it took one hand to push down my hard-on."

"When I was in my 50's, it took three fingers to push down my hard-on."

"Now that I'm in my 60's, it only takes one finger to push down on my hard-on!"

"So what I'm basically trying to ask you is? How strong am I going to get?"