As a mere leisure cyclist I thought I was pretty unfit. Until about 2020 my max in a day this century was about 70 miles, and that was a struggle.
In 2020 I discovered recumbent bikes. I found as I went further afield that though I wasn't any faster, I was able to keep going all day without any ill effects. So since 2020 I've been increasing my range, and last year I managed a century ride. I hope to stretch it a bit further this year. Since I'll be 74 next month I can say fairly confidently that I can ride my age in miles. It's as if I've discovered a magic fountain of youth. I haven't ridden these sorts of distances since I was in my late 20s / early 30s when I was quite an active cyclist. I do get a feeling of achievement doing these rides. I'm a solo rider, and enjoy the experience.
As an aside, I'd never heard of Eddington numbers until a couple of years ago, and that was a couple of months after I'd disposed of a load of old diaries with a lot of information on all the rides I did during that period -CTC diaries with weekly mileages, club runs, tours, YHA weekends and the like. I was extremely annoyed about that. I'm pretty sure that it would be in the 70s but based on the evidence I've managed to scrape together after hours of scratching about from other sources, my verifiable lifetime number is 55. Since most of my utility rides are a lot shorter than this it's going to take a lot of dedicated rides in the longer days of summer to increase it by any amount.