I save my orgasms for when we have time to take time, but I still love those hot little quickies. When my partner has blown a load and lost his erection, I feel free to continue with my vibrator to have my one or more orgasms. As for multiple orgasms, they're nice, but lately I prefer riding the after shocks of pleasure like riding a sexual wave without coming again. All those thrills and chills are every bit as delicious as a full-blown come and they last longer. I can stay in a heightened state of arousal with my vibrator for as long as I leave the switch on.
Physical exhaustion signals the end.
Personally I enjoy the feeling of being exhausted after sex. However, I would be just plain old tired if I had to provide his or her orgasm all the time. That's like a job without pay and that leads to resentment. Let go of those romantic scenarios that require mind reading that leads to pretense. Each of us needs to be in charge of our own orgasms.