Castle 2200 on 4s or 6s

So it seems the general concensus is that 4s is gonna be the best option for everyday driving.Geared for around 45 you should be able to run this thing all day.

No worries, anything equal or less than 165 degrees has no negative affect on the motors.

So what would be the sweet spot for temps?I know that as they warm up there efficiency seems to increase,till you hit the point that temps start to hurt performance,what point is that? My hypothesis is around 140.