> I’ve certainly had people visit who think of themselves as fit and they get gassed out by regular New York walking life

It's interesting how things become normal once you do it every day. I used to live in a fifth floor apartment without lift. Quite a few stairs to climb. Three things come to my mind.

a) You very quickly learn not to forget anything when leaving the house.

b) There is some perverse sense of satisfaction in having guests over and walking up the stairs together; and purposefully keeping a calm breath whilst the guests are wheezing and complaining.

c) Some tradesman was working on one of the floors. I will never forget the sight of him carrying something heavy up those stairs whilst practically breathing through the cigarette in the corner of his mouth.

For very legitimate reasons life like this is not for everybody. But I would say for able-bodied healthy people it would be good to have a bit of regular forced exercise like that.