Once.
I did it...once. I was in my 20s. We did a round trip hike from Curry Village to the top of Half Dome and it was a killer day. My legs were rubber at the end of the 16 miles and 5,000 vertical feet. Back then (late 70s), you didn’t need a reservation and there were no crowds. Now you don’t get on the cables unless you have a reservation and those are now hard to get. A close family friend is doing HD next week with some girlfriends. She is about 60 and in excellent shape.