J.M.
Well, I'm a "once a day" kind of girl, and my husband is a "once a week" kind of guy. All I can tell you is that I'm willing to "float" him a lot more stuff around the house when we tend towards my end of things (Didn't do the dishes? Ok. Need to work late? Ok.) It's not a "trade" - man, would it feel lousy to think that he was having sex with me to get out of doing the dishes! But I guess it's just more that I feel like some of my needs are being met too.
And, not to be obnoxious, but don't look a gift horse in the mouth. If the sex is reasonably decent - enjoy it! My husband is undergoing treatment for rectal cancer, and it's been eight long weeks since I've gotten any nookie at all. You never know when you're not gonna get any - enjoy it while you have it!