I'll disagree as most writings of the cruising lifestyle point towards just the opposite...it's a healthy, not sedentary lifestyle...I have to agree as many days I'm pretty tired at the end of the day from pushing carts up/down ramps full of groceries, etc....scrambling around decks to tie up, anchor, launch the dingy, haul the gas cans...ok so it's not bricklaying but then maybe it's how you cruise.50 is too old for some people. 90 is fine for other people. Depends on health. Trawler cruising is pretty sedentary (sailing is more active), and in general a whole lot of strength/athletics is not required. On the other hand, squirming around in the engine compartment, pulling an anchor, and the occasional unexpected emergency (Murphy's Law is in full force with all boats!) can be stressful.
John
Days spent boating are not deducted from the sum total of your life!
There are a lot of guys in my yacht club who are in the final stages of making that walk.
A guy I used to race against in Chattanooga is 92 and still kicks the butts of most of the non-spinnaker keel boats in our club (including mine before I stopped racing a few years ago). He was taking firsts in a very competitive club racing environment as recently as last Sept. and shows no signs of giving up.
A cool side note: he was shot down over Germany during WWII and spent 6 months as a POW. One of his closest friends at our club (until he passed a few years ago) was a former German soldier who'd been a POW over here.