I had the cherokee flushed at about 100k and have changed it a time, maybe two since then with filter,,clock is ticking 190k plus.
Pulled a cooling line off the dodge, brush busting and pumped a bunch out, did a roadside re-fill of 5 quarts, in the dark at about 10 degrees outside, still wasn't full, had a load of wood on it, got me home. Another 4 quarts later, , it was full again..have changed filter/fluid a couple times since then because I work it pretty hard and once to adjust the reverse band this past fall, which worked wonders!!
I think all fluids break down and need serviced. I am a fan of synthetics.
The flushing deal is supposed to remove tarnishes and sech,,I dunno...