A local rider here turned 70 recently. To ‘celebrate’ on his birthday he rode back and forth to the next town (10 km each way) 7 times. Thing is, the next town is also 600 M (~2000 feet) lower than our town so he rode 4200M up and 4200M down that day. Lots of it on 8 to 10% grades.
He’s hardcore crazy imho!
Mind you, his son was an Olympic athlete....