Buying a Former Rental Class C. How many of us out there?

From my limited experience with, and reading the post on it, my conclusion is that it is great to have on when there is a up/down grade or when towing.
In mostly flat highway and the like, having it off seems to let it get better mileage because of more efficient shifting. I will keep an eye on trans temp now though... Overdrive usage could be heating the trans like others have reported.