Let me also add that there ARE exceptions to my experiences:
My sister in law's sister started dating a guy when she was 18 who had been married twice and was 43 at the time. Her parents went nuts. Her Dad told me if he could have figured out a way to kill the guy, he would have. Her Mom said it was the only time she ever seriously considered suicide. It was a mess.
That was 25 years ago and they're still together

He's an incredible guy and I honestly couldn't imagine the two of them NOT being together.