I can't speak for the guys who have been "married" for 22 yrs (whoa) but I have been in relationships that lasted 6 yrs + and been totally monogamous the whole time with every one. In fact, when I'm with someone I find them as attractive (sexually) on the last day as I did on the first. But that's just me.
Yes, it is common (almost a golden rule) that sex goes out the window 2 minutes after a woman hears the L word but that only indicates that you TWO have something to work on. If she isn't interested in finding out why? Then I leave...plain and simple.
Sorry, Mongrel, you may feel that a good sex life isn't a major part of a relationship but to me, it is 1/3 of it. I don't care how good the other 2 are, if there's no sex, then there's no relationship. For eg: if a woman didn't love you would you stay with her? Nope. If she started doing stupid things like spend all your money on Cardboard buildings would you stay with her? Nope. So why stay in a sexless marriage?