My personal fastest 24 hour split was about 600km, while riding the first half of the Paris-Brest-Paris brevet in 2019. I had my first sleep after that in Brest and took much longer breaks for the return journey for a total ride of 1240km in 78:02:21 (with ~26 hours spent stopped).
I'd done many 600km brevets before that comfortably in 35-37 hours with a ~4hr sleep in the middle, but at PBP there were thousands of other strong riders and it was fun to work together.
https://en.wikipedia.org/wiki/Randonneuring is a lot more "normal" of a way to ride your bike all day than the Ultracycling approach in the article. Instead of grinding out laps of a racecourse solo, ride from town to town on pleasant backroads socially.
I'd done many 600km brevets before that comfortably in 35-37 hours with a ~4hr sleep in the middle, but at PBP there were thousands of other strong riders and it was fun to work together.
https://en.wikipedia.org/wiki/Randonneuring is a lot more "normal" of a way to ride your bike all day than the Ultracycling approach in the article. Instead of grinding out laps of a racecourse solo, ride from town to town on pleasant backroads socially.