old age
If you're a guy, take your penis out of that girl's vagina. If you're a girl, push him away!
Sex is over usually when the man ejaculates. It's sort of a physical limit. After that all the guy can do is cuddle (if he is willing to).
When both parties are significantly pleasured and/or tired.
Most of the time one person or the other or preferably both climax or orgasm. women can mostly orgasm a number of times before sex is done, some not so lucky, Most the time sex is done when the man...