Pretty much this. ^ DH and I (together 35-36 years, both nearly 60,) have had some ups and downs in the past - and I have had times when I have felt like walking, but our children have kept me with him. We had a very bad patch for about 4-5 years when they were very small, but AFAIK they didn't pick up much - if anything at all. (If they did they never said.)
For the most part though, the 36-ish years with DH has been good, and especially for the past 12-13 years. We are comfortable financially, and-mortgage free, and have no children to support anymore - they left over a decade ago - and being financially comfortable helps. Financial problems can cause more issues than most other things in a relationship.
Like you and your DH @mikado1 my DH and I get on really well these days, and are more in love than ever. We never argue, and we have a good laugh together. We have someone to laugh with, to cry with, to go for a meal with, to go on a daytrip with, to go on holiday with, and to share life's trials and tribulations and burdens with. I see no point whatsoever in leaving, (even if the marriage is a bit dull and boring, which ours isn't by the way!) And I can only surmise that the women who do this (leave their DH when they're 50+) are very VERY unhappy. Because there would have to be a lot wrong for me to leave.
I have seen women leave their husbands over the years, (at 50+) and they end up having to work every hour God sends just to pay the bills. And they'll be working til they're 70! I am nearly 60, and I work part time (16-18 hours a week) and have been part time since we had children (30-ish years.) I am retiring at 60. (So is DH.) I could not have stayed part time since 29-30 if I had been alone. We are much better/much stronger together. DH's wage would be enough for us to live on if I didn't work, so my wage is surplus money/pin money.
I have seen too many women 50+ leave their DH, and struggle to make ends meet, and be thoroughly miserable and worn down, and age much faster than me with the stress of trying to survive. Of course, some women will come on here now and claim they are much happier since leaving their DH, and are loaded/have a better, more well paid career than him/more friends/a much better life la la la. But in reality, life will be very difficult on her own - for most women.
That said, if DH and I did split, or if he died, I would have NO interest in being with another man. I would just stay single. Couldn't think of anything worse than having another man in my life! shudder! 😖 The dating pool for men 50+ is as lame as fuck.