We ran the T-IV in our '03 4Runner to 100k miles per the book. It looked fine on the stick just before replacement. 140k miles odo now and still shifts like new.
My neighbor had a recently-deceased Dodge extended body van which he ordered new. He never ever changed the tranny fluid. The van died with 540k miles on the odo. The whole drivetrain, all original and never wrenched was still operational, but the front suspension collapsed near his home so he junked it.
Some AT's are 'dirty' and need frequent fluid changes, and some are not.
My neighbor had a recently-deceased Dodge extended body van which he ordered new. He never ever changed the tranny fluid. The van died with 540k miles on the odo. The whole drivetrain, all original and never wrenched was still operational, but the front suspension collapsed near his home so he junked it.
Some AT's are 'dirty' and need frequent fluid changes, and some are not.