After I cum, I suppose I COULD keep going if I forced myself, but it doesn't feel good. The intensity of the sensations in the head of my penis post-orgasm is beyond description. I usually stop thrusting when I start to cum, and stay in her until my orgasm spasms stop (usually 30-60 seconds) and then I SLOWLY pull out.
When I was in my 20s, I could start back up after just a minute or two; now I would have to wait 20 minutes at least. But we don't start back up. My wife only cums from oral/fingering, which I give her as much as she wants (usually A LOT) before intercourse.