BTW, I am coming up quickly on 75. I am in the middle of replacing 5 Lifeline 8D batteries, single handed. Old have been removed and one new is installed to maintain 12 volts, just in case, as I take advantage of all the space available to do other maintenance. I have definitely found that as the muscle decreases, more creative engineering thinking is required.
I also deal with a personality trait called perfectionism. Makes it hard to subcontract work. I have taken a few steps down this road, hiring out boat washing, bottom painting, and exterior detailing.