One thing that kills marriages today is the parents become the full time extra-curricular directors of their kids. This kid to soccer at 9am, the other parents takes the other kid to softball at 9:30. The first takes the first to scouts at 11. The second parent takes the other to some other club thing, etc, etc, etc. This goes on all weekend, not to mention the gobs of money parents spend on long trips for traveling club baseball leagues.
By the time these kids grow up the two parents are left with nothing but themselves which evolved into two strangers living under the same roof. Believe me, I saw this first hand with my wife. Once her little sister got married her parents divorced within months. Two people who had nothing in common, nothing to talk about, and did not even know one another.
Oh, and "staying together for the kids" doesn't work either. Even as a 24 year old married woman, my wife was devastated for a long time over her parents' divorce. In many ways it has played a part in how my wife and I treat our marriage. We have our kids in maybe one or two extra-curricular activity, we get in as much alone time as possible, even if it means sitting at Panera and talking about life over a cup of coffee. Best of all, "gram gram" goes back home to NoCal and takes the two kids for two weeks every summer so the wife and I go to baseball games, go rent a cabin in Gatlinburg, or whatever we can find to get away from this house.