I turn mine off full time while in town or when towing. The only time it is on is when I get up over 50 mph on the highway.

 

I do the same as dhvaughan , I have 3:55 gears so I turn it on at around 65 though. When I'm coming up to a hill on the highway I turn it off, so I'm not going up the incline like Grandma. I have done this all along and see no change in mileage, but atleast I have no probs with my tranny,Yet,LOL, knock on wood.

 

I never turn mine off....lol with my 33's and my 3.55 my tuner adjusted my O.D. so it don't kick in till 55mph and then my rpms are like 1400 at 65 they are about 1650 with O.D. Most of the time I can make it up a hill /o the O.D. kicking out. but on real steep grades i have to push on the gas a lil bit.

Idk if what I'm doing is wrong or right but its done good for me.

 

I turn mine off when I'm not on the highway. It does not only keep the trans out of O/D, it changes the shift points so performance is increased. If you want "more power" the easiest thing you can do is turn the O/D off.

There is a mod you can do to "reverse" the O/D switch so it's 'off' unless you switch it 'on'. I have not done it though.