I was with a guy who didn’t always climax, and I have to say it was kind of uncomfortable for me at first, for all the reasons already mentioned. When I thought it was because he “couldn’t” I felt like it was my fault. When it sounded more like he “wouldn’t” for whatever reason, I didn’t feel insulted, but I did feel irritated (physicaly and mentally). As others have said, women don’t necessarily want a marathon session, so if you “can” then do and if you have no intentions of it happening, kindly find a way to shift the activity to something else 
Cool! Now I’m an author of “bedroom material.”
There’s no way to tactfully ask to stop. Just suddenly stop, say that you had an orgasm, and that you’re just “too sensitive to be touched” anymore. If it’s your style, ask if there’s anything else you can do for him, or offer that you’d find it really sexy if he finished with his own hand.
Inigo Montoya writes:
I’m afrais I’m having trouble with this. Do you mean that you don’t have many orgasms? Or do you really mean that you’ve had a lot of orgasms , but didn’t enjoy most of them? I can’t relate to either one of those. I think I’ve enmjoyed every orgasm I’ve ever had, and can’t see how you could have an orgasm that wasn’t enjoyable.
If you don’t enjoy it, what keeps you going? Is it the hope that another joyful one will eventually come along? Or is it altruism?
I think his point is that while the orgasm is nice and all, it’s hardly ever the most memorable part of the experience. Truly, it’s about the journey and not the destination.
Ah…you’ve invoked my bitterest smile. If you only knew how much I love and hate sex…
My stalker has divined my meaning as intended–I prefer the 1 to 20 minutes leading up to orgasm SIGNIFICANTLY more than the 2 to 4 seconds of spastic prostate and ensuing cleanup.
As a female who knows something about this… yes, I heard it from a friend of a friend! I can tell you that her worries are likely along these lines:
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Concerns about sex always being a marathon session, as described already a few times in the thread. Sometimes a “quickie” absolutely fits the bill, both from the point of view of time pressures and the point of view of thinking, “Wow! He’s so hot for me he couldn’t wait!” You would do well to impress upon her that the “quickie” is still a big part of your repertoire. You could do this by offering her one-sided only sex, where she gets her quickie orgasm (I am assuming she does not also have delayed orgasms) and you get nothing but the joy of helping out, or two-sided sex, where she gets her quickie orgasm and you stop as soon as she’s done. If she asks, “Are you sure?” You should reassure her at length that you had a great time and are happy as a clam.
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Concerns about “why” you can’t come like a racehorse every time. Is she doing something wrong? Is it some sort of control issue, where you keep yourself detached much of the time during the act for reasons only known to you? Are you perhaps embarrassed about the face and the grunts you make during orgasm? Do you come all the time when you masturbate, but not with her? WHAT IS IT? She will want to talk to you about it, and you should remain calm and give the answers good-humoredly and reassuringly.
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This is related to 1), but MAKE SURE you set up some communication that allows her to call it quits when she’s had enough. She is probably quite happy to bang or slurp away for long periods, but there will be days when she won’t be, and you have to make it clear that you WANT HER TO TELL YOU, and that she doesn’t always have to hang in there waiting for the elusive orgasm that may or may not be coming (ha!), even if it looks and sounds like you’re having fun.
I’m glad I was able to remember everything my friend told me!
“I do not avoid women, Mandrake. But I do deny them, my essence”
Tell her its about purity of essence and bodily fluids being too precious
Many guys say this, but it doesn’t apply to some of us, like me. While my scale might not go to 20, it at least goes to 7. Quite apart from the physical sensations, an orgasm can be quite an experience depending on the… trying to think of a way to keep this non-TMI… let’s just call it the circumstances around the orgasm.
As for whistlepig’s problem, this is something you need to talk about, and not during or immediately after sex. Agree on an acceptable way to communicate when you’d both like to stop.
Word.
Male orgasm is like pizza. Even when it’s bad, it’s still good. But no matter which, it’s still only Pizza. For women who experience multiple orgasms, it seems like a multi-course gourmet meal.
The seduction, the prospect of inevitable sex and the actual kanoodling is far more intresting and exciting than the climax, which is often bittersweet because it signals the completion of something really good - at least for the refractive period.
My last bf was like this, very experienced, late 30s and it took a while for me to accept this.
His constant reassurance ( and erection 
) made this easier and easier to believe the longer we were together.