Just 8 months after buying a road bike I did a 4700m / 188km one-day event over 5 mountain passes. A new rider at maybe 2.7 or 2.8 W/kg, and having trained mostly on the flats, I was getting passed uphill by most riders even some guy in his 70s LOL.
Stuck to my 135bpm “can ride uphill all day” pace that I determined on three earlier 160km training rides in the nearby mountains. Knocked it out in 11 hours and 15 minutes (moving time). PR’d the final 14km of last 24km climb - 2 weeks prior we had ridden that portion of climb about halfway into last of the 160km training rides.
My HR on long TR intervals at 70% ftp is about 126-130bpm. Without a power meter I’m not sure what intensity I rode that epic 5 pass climbing ride.
Last year I did a 320km double century with 2520 meters climbing at 67% intensity (power meter) at 130bpm average HR and finished in 12 hours and 45 minutes moving time. Very different ride, no HC climbs on that one.