Why do some couples break up after being together for a long time, more than 5 years (what are the possible reasons)?

I mean, I kinda get it when a couple break up after being together for 1 , 2, 3 or 4 years, maybe they are not compatible and that's the time it took them to find out they weren't, or maybe they disagree on major things etc...
But otherwise, if you've been together for more than 5 years, it means you know each-other well.
Unless there have been a major change like, one of them started smoking crack or became violent and alcoholic , or someone cheated, I don't see why some couples who are are like married for 12 years suddenly decide to throw all these years and divorce/break up.
Why do some couples break up after being together for a long time, more than 5 years (what are the possible reasons)?
17
12
Add Opinion