This is a pretty broad question. I would narrow it down to:
- Early retirement when you are still fairly vigorous which I think would be when we are between 60 and about 75: (We traveled quite a bit, hiked, took cruises, did a lot of landscaping, rode my motorcycle, visited far-flung family members, remodeled the house, went to the gym or swam several times a week, participated in frequent potluck dinners where we ate too much, took in a number of shows on Broadway, got into Yoga in a big way, and took up watercolor painting.)
- Later retirement when a lot of energy has departed and various aches and pains start to need increased attention. In my case this started around 76: (the motorcycle leaves, doctors appointments take more time, getting a good night's sleep doesn't always happen, the wife mandates that I stay off the roof, I start getting yard service, we start to go out for nice lunches rather than dinners, wine consumption takes a nosedive, travel overseas becomes rare, TV watching increases, reading decreases because of declining eyesight, and I had to start dealing with prostrate cancer.)
And then along came COVID19 which changed the equation even more drastically for all of us.
Your parents sound like they are in the later stage of retirement; cut them a lot of slack.