When first starting masturbating my cock was extremely sensitive. Just pulling back the foreskin (yes, I'm happily uncut) was a mix of pain and pleasure, and to actually JO was even more of that. I couldn't keep doing it long enough to actually cum. But one time I just pushed myself to keep going and I ended up having an orgasm that made me almost faint. My legs were shaking and I was unable to stand up. From that day I couldn't stop.

My cock was still very sensitive but the oversensitivity decreased with time. However, after orgasm, my cock was super sensitive. Too painful to keep stroking.
Being in my fourties, my sensitivity has decreased to the point that I can control my pleasure and go on after the cumshot. If I do I most often shoot some more fluid. Not cum, but maybe cum-fluid? I don't know? Anyone else do this?
The sensation is very different. It's more like really emptying the cock to the last drop, but without the over the top sensation in the orgasm.
Sometimes I miss the days when I was as sensitive as in my teens, but being in charge of the cock is amazing too!