I once experimented with this while masturbating. When I was about to cum, I pinched off the end of my dick and waited about five minutes. When I let go, some cum shot out but the total ejaculation was maybe about half of what is normal for me. I guess some went back down the pipe. Of course I had to masturbate again to flush out my pipes about 45 minutes later since I didn't want that old cum in there. I *** you not, my ejaculation then was much more than usual. I guess the new stuff combined with what was already in there for a super spurt! Thanks for putting up with my story.
BTW-Pinching off your dick for five minutes when you're about to cum doesn't really hurt, but it doesn't feel really good either, and you have a sucky orgasm. If you're thinking of trying it. :dunno: