I always let it down shift as it needs too. I assume that's why it's called Automatic. Now if I come upon some slow traffic going up hill I slow down and shift it down.
We had a couple we use to travel with, every time he came to a hill no matter how steep the hill he would shift it down to now matter what his speed was. Every time he did it the blue smoke came out from under his MH, I asked him why and he would reply he was getting a run for the hill. I know of 2 transmissions he replaced. I guess to each his own.