horses for courses.
Tell you what though, when I get a bit tired, find myself fighting a cross wind or a long incline I find myself, rather than slowing down and grinding, eeking out all the efficiency I can by smoothly applying power all the way through the pedal stroke, getting into the most appropriate position e.g. aero for battling a headwind or upright and relaxed for a climb and I'm really happy with it. I find the art of keeping that gear spinning at over 80 rpm quite satisfying.
I know I can spin fast.. that is what sprinting and descending are for.
I don't want to grind and knacker my knees up. The only reason I would gear down now is if I lost fitness.