Well I'm sure this marriage had a lot of issues. Age difference, celebrity, step-children, 2 career couple, small child...any one of those is enough to cause a lot of marital stress, much less all of them together.
I had the tremendous luck and honor to meet Paul & Linda McCartney for about 30 seconds back in 1992. I was working at the Barnes & Noble Booksellers in Tucson, Arizona, when they came into the store. I thought I was going to pass out! I am such a huge Beatle fan.
The area of the store that I was in charge of included cookbooks, and by some stroke of luck, my current display was devoted to vegetarian cooking, and featured Linda McCartney's cookbook.
They seemed like a very happy couple, I imagine it is not easy to follow in the footsteps of a long and happy marriage.