I don't consider it moral for two people to make each other suffer for years instead of admitting their mistake and moving on with their lives. That's the result of pride, not forbearance. Still worse if one party suffers while the other remains pleased.

If there are severe practical obstacles to divorce then that's one thing, but even then there are ways around that. It's nothing unusual for a couple to separate while remaining married. For example, Warren Buffett had such an arrangement for nearly 30 years--until his wife died.

So now I'm praying for the end of time
To hurry up and arrive
'Cause if I gotta spend another minute with you
I don't think that I can really survive
I'll never break my promise or forget my vow
But God only knows what I can do right now
I'm praying for the end of time, It's all that I can do
Praying for the end of time so I can end my time with you

--Meatloaf