I'm in my early mid 70's. I hand split for about 40 years and felt pretty smug about it. It impressed the young guys but the older, wiser men would just give a wintery smile and shake their heads. I started having upper back and shoulder problems. When I got a splitter some 7 years ago I was amazed at how it changed wood splitting. Still a chore but not so damaging to an aging body. The proverbial "Why didn't I do this a long time ago?" for certain! You will also gain so many friends: "We took a tree down last week, why don't you come over for pizza Saturday and bring your splitter". In all seriousness, I can't imagine home heating with fire wood and not having a splitter! It may well keep me heating with wood into my 80's like some Ancient Ones on this site! to my Older Brothers.
Mid 70s here, in undeservedly good health. I gave up splitting by hand 15 years ago, after a particularly energetic session gave me tennis elbow. After getting a 5 ton electric splitter, which is sufficient for my needs, I built a stand for it, which brought it up to truck bed height, eliminating all of the associated bending. Then I put a hoist in the back of my truck for lifting big rounds. After that I converted the hoist from manual (which was painfully slow) to power. Once the rounds are in the truck, the wood never touches the ground again. I split into the wheelbarrow, thence to the stacks. I still get plenty of exercise bucking and rolling the rounds to the truck, then rolling them onto the splitter. If you want to keep doing this, you just have to adjust you technique to your diminshing capabilities.
I pretty much agree with everything you are doing and all you said. I am 72 and had rotator cuff surgery (left shoulder, I am right-handed) about 22 years ago. I am mostly ok but it will flare up a bit now and then. I still enjoy some hand-splitting but like someone said in this thread, just the easy stuff, lol. I enjoy doing it. I asked my brother to bring back my X27 as I let him use it and I have been using the Fiskars mauls but I think I prefer the x27. I'll tell ya after I use it some more! I bought a hydro splitter and it allowed me to do more, faster. Much more. I think a little hand splitting is good for a fellow as long as the shoulder/back allows one to do it. Any kind of exercise is good, especially something that involves heavy weight. Just moving heavy oak rounds around is a good workout! Splitting, stacking, firewood is good, hard work. Do all you can till you can't but don't overdo it.
I like your set-up! "You have to adjust your technique to your capabilities" is such sound advice. Lots of ways to do most things if you put some thought into it, if you truly want to do them.