How coincidental and timely this thread is. I too have noticed a drop in my maximum comfortable RPM. Over the last several years. And even for the last year that I was in good cycling shape.

I've been thinking intervals of just going into the 120's and 130's for as long as I can might help. And gearing down to super ridiculously low ratios so that I keep my power (watts) reasonably low too. Or just riding the entire ride in that same super easy gear combo that keeps my cadence high and power lower than normal.

I haven't worked toward that though as I'm not riding enough this year. But essentially that is what I did to get my cadence up over the 75 RPM average that I had plateaued at 3 or 4 years after starting to ride for fitness in my early 50's. Doing such got me to where I'd sometimes look down and find I'd been cruising comfortably at 100 RPM for a time thinking I was back at my comfortable 80 RPM. It also seemed to work especially well when I began my cycling season late February and March doing those type rides. November through January and into February, I'm a real slacker on cycling. Even next week they are showing way too cold for me, temperatures in the 70's here. I'm likely to freeze! <grin>