The first time I was able to retract foreksin during erection, (I was 10.5 years old), I had my first wank. I reached perhaps my most intense orgasm. I didn't ejaculate, so I didn'T really know when to stop, so it got to a point where it was so sensitive it hurt.
When I was 20, just before my first circ, this was nowhere near like that. But then again, ejectulation would provide the hint the time to stop was coming, so you'd avoid the stage where it is no longer pleasurable because sensation is too intense.
I think that with time, one learns to control the wanking to avoid reaching the post-ejaculation spot where it is too sensitive to be pleasurable.
Consider this: whether circumcised or not, the increased sensations during/post orgasm are in the head only. The glans doesn't suddently grow more nerves just for the orgasm.
So I would think that the brain simply learns to moderate the excessive sensations post orgasm to avoid uncomfirtable levels of sensations.
Going from semi cut to fully cut, I switched to rubbing head/shaft instead of sliding skin/up/down and I find that I can get stronger orgasms because I have more direct stimulation of head than when I was semi cut.