For the first 2 1/2 years she really turned you on, that's what we call "being in love." After 2 1/2 years, not so much. That's why there has to be much more than sex in a relationship...real love and caring for the other person, along with a big dose of realistic expectations...so it will hold together when sex is no longer the center of the universe. : ) Or when the sex begins to get a little boring, which is when people like to say they "fell out of love" in order to justify finding someone new to have sex wtih. : ) Love has nothing to do with THAT.
Yeah you pretty much nailed it.
And this usually isn't that much of a problem...people move along, find someone else to fall "in love" wtih. When it becomes a problem is when there are children involved. Couples who want to have children need to make that conscious COMMITMENT to remain together after the lust has died down. So they need to make sure they have enough in common, shared goals, etc. and genuine fondness for each other before they start popping out the kids.
Unfortunately, too many people don't approach this with the care they should. Therefore, an unprecedented number of kids today come from broken homes. It's sad, really. And people can rationalize all they want, it is very, very hard on kids. Except that so many of their friends have broken families that the stigma is less than it used to be. : (