There are some guys whose glans become super-sensitive just after they orgasm; I've been fortunate to have a couple as edging vicitims. I can put them in quite serious pain without doing any physical damage by continuing just exactly as I did before they squirted - until their dicks go completely limp. <evil, sadistic grin>. Of course, this isn't edging, it about how the session might end. Apologies for going slightly off-topic.