I'm in my early 60's, but it isn't getting any easier, that's for sure.
I shot elk and packed them out solo in two different states this year. I set up a spike camp about 3 miles from the trial head and spent 18 days hunting from there in September. Several times I turned away from bugles when I was about 5-6 miles in from the road, and the elk were even further, and just realized that packing a big bull out solo that distance in the heat would not be practical. It hurt me to turn around and walk away, but I'm pretty sure it would have hurt a whole lot more had I been successful that far in!
I can still go pretty hard, but my recovery time is longer. The third 15 hour day of packing heavy loads just isn't an option. The first day is fine, but painful, and at the end of the second day I simply have to take a day off. It sucks, but that is the reality, at least for me.
I have to say that this year in particular I spent far too much time in the back country, trying to figure out how many more years I can still do it. I believe I still have at least 5-10 years, but that is beginning to seem damn short. If I got help with the packing I could probably extend that another 5 years at least - or so I tell myself.
In any case, I will still keep going in as deep as possible until my knees finally give out. Whether that is next year or in 15 years, it is impossible to say. Live for the moment!
Bill