Don
Not tested to compare but I have used it with it off for the better part of 3 years.
I also only charge it up to about 80-90% and i can get 24hrs from them before it hit like under 20%.
I don't need the screen to be on when i am not looking at it.
That was my logic, just sometimes (mainly in bed), when I raise my wrist, it doesn't trigger the movement, and the absolute agony of doing it again made me think I should be utilising the technology of always on