You yourself said that 20 minute intervals were the bread and butter of the greats of yesteryear...
Not entirely, if you reread the quote in the message.
Lemond seems to think that long intense hours are what you need to keep your levels high, I think Merckx, Hinault & alot of others went by the same means. That means not maintaining a certain power output for a certain day, it means high intensity, every single day you ride, everyday. I doubt very much "recovery" rides were ever on the agenda. I couldn't allow myself (If being a professional cyclist) to train at 250w when there were guys out there training at higher wattages every single day. I would feel like I'm short handing myself.
I know one mental tool I use every single time I ride & that its never to let the motorist see you ride slow or see you weak. It keeps the intensity sky high for me.