Dave:
Your premise is, at least for me, not valid.

My use of high speed is primarily for backwashing. When I used a hose vacuum, I would need it then. But now with autocleaners and a PoolBuster, the hose vacuum's been the cellar for 2 years.

I have solar panels and they work well with low speed. They ARE more efficient at high speed, but if the water is warm (89-90) why bother?

I sometimes use high to circulate the water more--to make the skimmer more efficient or distribute chems faster. But generally, low is JUST FINE.