AU 4speed Auto Question ?

[XR6-VCT-2000]

Just wondering if those of you out there with automatics leave the car in 4th gear ( Drive ) while driving around local streets or city streets etc. (doing around 0 to 80 kmph )?
Recently i have found myself leaving the auto in 3rd while driving around under the speed of about 90kmph, otherwise it's constantlly changing between 3rd and 4th(D) while doing low speeds, not only does it change gears more often but also seems to use more fuel doing slow speeds in 4th(D) too.
On this topic - I had an old crapbox a few years back that had an economy meter in it, If you did low speeds in like 4th , even though the car was almost idling along , the economy meter would be up the creek, as the engine allthough reving low would be working its nuts off to push the car along at low revs/near idle . I allways seemed to find that keeping the engine around the 2500 rpm / right on the edge of responsiveness / cruising along / would use stuff all fuel and the engine would just purr along.
Imo i think they should of just left 4th(D) on a button on the t-bar as an overdrive button, as thats all it is really, doing like 60kmph in 4th (D) is as useless as titts on a bull - as the auto is forever changing gears and 4th has no usefull power or real gains at that speed anyway.

Does anyone else on here NOT use 4th(D) much on there Auto's unless on freeways or 100kmph stretches and stuff ?