Together 17 years or so.
Now my last few months have been minimal but a new baby and such will screw that up, and I can't hold that to the norm.
The norm would be a minimum of once a week and a max of four but don't hold me to that. I'll still complain its not enough of course.
The lack of frequent sex I've heard of as a complaint from both men AND women. There must be something about me which tells women I know to tell me their sexual issues, but at any rate the lack of sex from the womans point of view has caused a divorce and an affair in the last year with two people I know (mind you are they internet 'friends' which would explain why they are more open and yea I know they are female
)
In both cases everyone was fat and out of shape. In the divorce case the woman was out of shape, told me how 'that wasn't the issue' since her husband never complained about it (directly, she seemed oblivious to his little hints) and after they separated he told me he should have told her she was unattractive to him earlier.
With the affair, they are both fat. She claims to be uninterested him since he let himself go but she in turn has let herself go because its not 'worth' it to stay in shape for him. So they are both fat and unhappy with an awful sex life. I don't know her husband like I know the other one but I have to wonder what his take on it all is. All she does is complain about how bad the sex is to me.
Now its not the fat per say that is the problem, its that they become unattractive to their spouse, fat is just the most obvious in some cases. I'm sure for some men its due to wanting their wife to always be that 24 year old they married, but for a lot of them its just lack of personal maintenance.
If you have been having sex with the same person for years, and now they are substantially less attractive then they used to be, perhaps completely unattractive, you can only expect the frequency to go way down and sex to become more of a chore for them.
Finally a side note: Sometimes I've heard of this and it seems that even early on in the relationship they were having sex rather infrequently. My feeling is that if when you first start to have sex you are not doing it like rabbits, but say are on the 1/2 times a month track, you can pretty much kiss off a sex life 10 years down the road. Desire will go down and if its already low, it will be damn near close to zero by then.