After reading the last several posts... I just wanted to toss in a thought that even when two people have been married a long time, it doesn't that their marriage is stable or even moral.
Some of my friends had parents that stayed together for decades and are still together, but they're in abusive situations or are having affairs and looking the other way.
I had one friend whose mother caught her father with his secretary, and he announced that he was going to do whatever he wanted, with whomever he wanted, and that she was just going to have to live with that because he brought in all the money. He thought he had her trapped-- he was bringing in a 6-figure income and she was a stay-at-home mom for their 4 kids, and she only had a high school diploma.
Her answer to him was basically, "You've got to be kidding, and so she left him, got custody of their kids (he had no interest in them because he wanted to keep all his money for himself), and raised them all on her own.
In contrast, I had another friend whose parents stayed married until the end--but their kids were regularly traumatized when they would come home from school and catch either parent with someone else, always with a warning that they were not to tell the other parent about the new "friend" who had been over to "visit."
Both of these friends were terrific people but I honestly have to say that the one from the divorced home seemed to be in a much better place emotionally.