I'm not going to jump on the judgey bandwagon.
I get a lot of it OP. At some point in a marriage, sex does tend to go out the window and if you are lucky you'll have lots of kisses, cuddles, snuggles and hand holds and it's lovely. A lot of women don't even get that on this board with their straight DHs.
One thing I would say though OP is that at the end of the day, none of us can fully trust anyone. Any of our DH's could have their head turned at any time. My own DH is up there with the best, but I still cover my own arse.
When all your DC have flown the nest, and it is just you and him, he may decide he wants to visit his true self and move in with a man he loves. He will have had all his needs met for family and DC. Other DH's do the same and run off with a 25 year old regularly on this board.
Please, please, make sure you keep your hand in work, that you have your own savings, finances, your state and a private pension sorted, a will, and that your name is on the house and your name is on any life insurances etc. If your DH really loves you, as you clearly love him, he will have no issue doing this.
At the end of the day, love is great, no matter what shape and form that comes in, but also at the end of the day, you are alone OP and you must make sure your security is sured up.