I had this happen once, many years ago. I was in Milwaukee, visiting a friend with benefits. The last night I was there, we went out, had a few drinks and went back to his place. We got naked and messed around in his bed. We ended up with us laying on our sides, me spooning him and fucking him. After I came, I immediately fell asleep. I woke up a few hours later, I was still spooning him, with his head laying on my right arm and my left arm holding him with my fingers near his nipple. I realized my dick was still hard (thanks to the cockring I had on) and it was still inside his ass. I started to play with his nipple and I kissed the back of his neck. He woke up and started moving his hips back and forth. His ass felt so great on my cock. He kept this up and about 5 minutes later, I came again, shooting load #2 inside him. I fell back asleep, still holding him.
I woke up early in the morning, because he was moving his ass up and down my dick. My dick was hurting because it was still hard and still had the cockring on. His ass felt great on my dick but I needed to take the cockring off. So I pulled out, took it off, then flipped him on to his back and started to fuck him hard. The first 2 loads were leaking out, making a mess. I pounded his ass for about 5 minutes before I started to shoot load #3 inside him.
This time he had to clean up, there was cum all over the place. He ran to the bathroom, cleaned up and got back in bed. I went to the bathroom to take a leak and then I got back in bed. My dick was still hard (it would stay hard a long time after I came), so he got back on his side, pulled me over behind him and then he guided my cock back inside his ass. We feel asleep like this. When I woke up a few hours later, my dick had finally gone down and was now resting in his crack. When he woke up, he did suck me to get me hard again and then he rode my cock until I came for the 4th time.