Maybe TMI ... my basic approach, developed when I was 18, is:
Freely consenting adults write their rules, though I hope they draw the line well before letting blood and doing violence.
If one partner is unhappy with sex, it's up to that partner to bring it up and get the other partner to work on it.
One partner can't complain about the other unless s/he's brought up the issue, and the other partner refused to work on it.
Can't go outside M for sex unless it's an honest, open M between freely consenting adults. If one's partner won't help solve an issue, the other partner has to either live with the live issue or D.
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I was highly influenced by a Playboy interview with a prostitute in my freshman year of college (1962-63 - no pill, a few years before the sexual revolution took hold). The prostitute said lots of her business came from men who wanted blow jobs but whose wives wouldn't deliver. I can't describe how much that turned me off - I resolved never to be that weak/stupid/whatever.
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I ran across what looked like a great book on having a good M with widely divergent sex drives...I just can't find the title or author, but if you think it will help you, look. You may find it.
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For various reasons, my W freaks out about sex. It was usually hard work just to get her to participate in foreplay. (She enjoyed sex, but feared enjoying it, IIRC.)
But ow forced her to initiate sex during the A. As a result, one of my requirements for R was that she had to initiate sex with me 'sometimes' (I didn't put a number on it, but I would have if I had to). It's worked out pretty well, and I recommend adopting this requirement if sex is an issue for you and/or your partner.
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I read the results of a study in Huffington Post a couple of weeks ago that seemed to make sense. The study seemed to show that people compare their sex lives to what they think others are doing.
So instead of worrying whether your sex life is healthy, you could just adopt the belief that 'Our sex life is healthier than most other couples' sex lives.'
(While you do that, though, I suggest talking with your W and working out something mutually satisfying.)
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I've never felt sexual heat. I've felt lust - sort of, 'Boy, I'd really like to get laid,' but that was before meeting W2b. With W2b/W I've just felt a tremendous need to get it on with her, as if my life and hers depended on it. (Oops - in truth, it's more like I feel the Universe depends on our getting it on. (No thanks are necessary, though. The activity itself is reward enough....)
I've never felt heat, but when the Stones brought out 'I'm so hot for you', it brought back unpleasant memories.