Cripes I hope thats not retirement age for hill walking
but it does creep up on you. I've noticed that 'hill fitness' needs to be maintained, at whatever level you require for your own personal endeavours. It use to be something I didn't have to think about but as I approach 'the age' a few weeks off can set me back a fair bit. Years ago I never 'trained' as in gym or running etc, none of that ever interested me (still doesn't), but luckily being a slight build (except a certain area around the waist line, that fluctuates
) I never had to do anything to retain enough fitness to enjoy what I loved.
As been said i don't think you can fight nature, walking the hills in all weathers teaches you that, but I'm sure there are things you can do, and must, as any sport/hobby is less enjoyable if you're suffering, and we all know that feeling, ie not having suitable gear on a bad weather day
You may need to set your sights lower, and I for one have started looking at places that I might never have done before. An old back injury appears to have returned of late (waiting to see an 'expert') but luckily it doesn't seem to affect me walking.
If you're a true hill loving person, then it will be what makes you who you are, and to that extent, yes fight it, as you'll miss it, and keeping going will maintain some level of fitness into those later years; you've made it this far and that is far better and more fulfilling than just staying home
Keep well