I'm an older backpacker and  mountaineer.  I'm in my early eighties and still get a lot of pleasure from my backpacking and mountaineering adventures.  But, I have to admit that my trips are not as ambitious as they were 40 years ago.  Staying fit for my hiking is much more  difficult now than it was ten years ago.  But the enjoyment is still there and I still manage to to get out and enjoy my walks.  Ibuprofen helps.