There are several serious backpackers on this forum who are past 75 and still going strong. One is planning to hike the Appalachian Trail soon (IIRC) and another is a regular visitor to the Wind River Range in Wyoming: perhaps they will add a. note here too. I'm another of the 75+ gang and I'm planning a re-hike of the John Muir Trail this summer.

I think that I can speak for all of us about aches and pains and other age-related issues and their impact on hiking: mostly it's not all that bad. One of the people I mentioned is a cancer survivor (I believe) and I had to recover after being hit by a car while bicycling in 2010. You just have to adjust your expectations to the reality of aging and deal with specific issues. Finding hiking partners gets more difficult as one gets older; not all seniors share this madness.

Good luck with finding a Sherpa. Most people struggle enough carrying gear for one but carrying it for two would be tough. Have you considered using a burro or llama? I believe there are outfitters that will rent pack stock to qualified people.