I do 4-6 110 mile rides each year, routine long Saturday rides, not organized centuries. I don't know how many times I've exceeded 100 miles annually over my riding career, probably a couple of dozen times. I'll continue to do those 100+ mile training rides 4+ times annually going forward. I do 75+ miles much more regularly, like 25x annually. I have more problems with things like hot spots in my cycling shoes on warm days on longer rides or neck pain. I wouldn't want to spend more than 7 hours on a bike (those 110 mile rides are typically rather hilly 7 hour rides). I will probably go 120-150 miles one of these days just to say I did it.