I have family who have recently separated in their early 70s and late 60s. They have been together over 40 years.
They are both much happier now (especially her! He was also letting her do all the emotional and practical running of their lives, til she had enough). And they have been able to still have each other in their lives, just in separate houses and doing more of what pleases each of them.
How would you feel if he suddenly got ill, and your next twenty years are spent nursing him? You'd have to have a solid base to cope with that .. otherwise it would eat you up with stress and resentment.
Life is so very short. Once it's wasted, you never get it back. Listen to what you need, even if it disrupts the status quo for others. Your needs and wants are valid, and you deserve to live your life for yourself as you wish. It doesn't even mean you don't have to love and care about him any more. Just that it's time for you to listen to yourself, prioritise yourself, now.
Long ago are the days where women were consigned to the scrap heap after 40, to just deal with whatever, because they had settled. We can shake up that narrative. We can own our lives and our precious time on earth.