I was not really a 5 hour century guy at any age, much less post 60. At 51 I did 100 miles around the Indianapolis Motor Speedway during Tour de Cure in a tad over 5 iirc. Pre GPS so no data. Perfect conditions, dead flat, no navigation, aero recumbent, not much drafting.

I do see a 5:55 century last year, day 1 of Seattle to Portland. Shamelessly drafted a younger friend all day.

I count 113 rides over 100 miles since 2020, due to randonneuring. None terrible fast