My personal observation: As a women, the more I get sex, the more I crave it and when there are long breaks with no sex, the easier it is not to have it (some of my friends have said the same thing). When I have a long break without sex, I have to mentally phsyc myself up to welcome it again. Of course, this now adds a guilt factor because I feel that I should want sex, but I'm not in "the mood". I have to override my mood and just do it. Once things gets started again, I'm back to craving it.
Now no sex and no masterbation - I just get down right grumpy, bitchy and irritable. It's as if orgasams keep my brain chemicals balanced. Too bad it took me so long to realize this.