As I was reading your post, my first thought was that perhaps you've really grown to like this lady and that the sex was a turnoff because you really want more than that. You spoke about looking forward to seeing her and having a great time talking, but you also mentioned the time limit and feeling shallow and meaningless. Then you gave the impression that you got a bit of a "charge" by the facial, something you don't normally do. That makes me wonder if you've just gotten into a sexual rut with this particular lady. I've heard so many friends talk about sex falling into a routine and becoming boring. Do either one of these scenarios describe your relationship? If it's the first, that sounds like trouble. If it's the latter, then you just need to spice things up.

Re:When do you know it is time to quit?

Sounds like she's your wife of several years..You like her, but the sex is boring, try someone else..

Sexual pleasure is always wonderful. When you fail to feel pleasure, especially with someone familiar and special then you must look elsewhere for the problem. Are you spending money you should not? Have you begun to isolate and withdraw in other areas of your life? Are you drinking too much or using coke, speed or painkillers? If you begin to loose the thrill of being with a woman, perhaps there are other issues?

Thanks for the advice.  It could be a little of all those things, except for the emotional involvement the provider. Not at all interested in her for anything other than sex and a little short time companionship. But I don't want to get where I need to push the envelope too much to enjoy.  Ever notice how most mainstream porno now was considered out there just a few years ago?  Do you ever want more and more from your encounters, more than what most ladies are comfortable with?