I just discovered your book a week ago and I like your thesis. I'm already into sex without ejaculation and valley orgasm, so the benefits of that are not new. What is new is the discussion of the hormones of sex.
This evening I found an article on a new finding concerning prolactin:
"Surprisingly, after orgasm from sexual intercourse, the increase in blood prolactin levels is 400 per cent higher in both sexes compared with after orgasm from masturbation (Biological Psychology, vol 71, p 312)."
I find a couple of things interesting about the article. Instead of the negative connotation you guys give prolactin, they link it to a feeling of satisfaction. Something to reflect on. Am I depressed of satisfied after orgasm? The difference might have to do with context. If I'm unhappy with my circumstances, I might be depressed. But if I'm happy with my pre-arousal circumstances, I might be "satisfied."
That difference in circumstance might explain why masturbation leads to a more depressing orgasm, for me anyway, even though it leads to a lot less prolactin in the blood.