Life in a modern-day developed economy is quite long. If two people can be happy together for 38 years, during which time they raise a few kids, and then maybe be unhappy for two years and wind up realizing they want to get divorced is that really such a “failure”? It sounds okay to me. Kind of impressive, actually! As a society, I think we need to cut ourselves some more slack about this kind of thing. Failure is relative.
No. Divorce after 40 years, even if 38 of them were happy, is not only a failure it’s a tragedy. It doesn’t matter how many years the couple have been married or who they may be.