I’ve always been told if you don’t change the fluid before the transmission has 60k miles on it, don’t change it at all.
But, if you change it before 60,000-you can keep servicing it.
I’ve got a truck that I bought with 72,000 miles and have 270,000 on it now. Original transmission and haven’t done a thing to it except add a 2oz tube of shudder stop to it at 168,000. Runs fine.
