Since I've been messin about with boats, mainly professionally, since I was 12, I've found the biggest problem as I age is using my brain instead of my brawn when I want to do things I've been doing almost daily since I began boating.
My first major injury came when I climbed a dock ladder w/a scuba tank in my right hand, using my left to pull me up the ladder. I'd done this a gazillion times before! This time, the tendons connecting my bicep to the elbow let go. I felt them go and knew I was going down so I threw the tank clear so at least I landed on a flat deck, not the tank. I called my dad who was a surgeon and told him of the injury and asked what medical care I should seek. Part of his response was, "You dumb sh*t, you're 60, not 30, start using your head!".
The next, but much less serious, injury came from overshooting my mooring, just a bit, in Honeymoon after returning from fueling in the marina. I couldn't possibly count the number of times I've grabbed moorings on boats even bigger than Skipping Stone (53'/77k#) and just held on until they swung and dropped back so I could secure the mooring line. This time all the muscles involved gave me fair warning that this was not something they were willing to put up with and the next week was spent in agony.
One thing that I have going for me is that my wife is much, much younger than I and truly loves sailing. She is physically capable of doing any job aboard, not giving any thought to the silly "blue or pink" nature of a job. If it's to be done aboard she will happily do it.
I doubt I can put a number on when sailing will no longer be possible for me physically, but it surely won't be the end of our lifestyle, when (or if) it happens. My wife and I have discussed the motor boat thing, with some excitement, for there are a great number of cold places to explore that would be a lot more fun from a heated pilot house, in a 3k helm seat, than an open cockpit.
