I sort of agree.
If the fluid has NOT been changed and the tranny shifts fine and the fluid smells and looks fine LEAVE IT ALONE...
If the fluid has NOT been changed, but looks brown and smells bad, change it because the fluid has had it's additive package burned away and is contaminated which WILL lead to failure.
Clutches, bushings, bearings, gaskets etc all wear and while much of this *Stuff* ends up in the filter, a lot of it finds it's way into various knooks and crannies of the valve body where it very well may sit there for years without causing harm.
What happens when you introduce new fluid into a tranny in that condition is that the fluid acts like an enema for your tranny and now that *stuff* that was lodged in places where no harm was done can potentially be released and find a new home lodged in a place where it CAN do some harm.
This is because the fresh fluid has a new load of detergent additives in it.
This is why trannys sometimes go up in smoke after a fresh fluid change.
Bottom line, if fluid smells good, looks good and you have not changed it in say 100k miles, leave it alone.
If fluid looks bad, smells bad or you are having problems, change it because the old fluid is not protecting your tranny.
For the record, I have a 92 Caprice with almost 500,000 miles on it and have never changed the tranny fluid or filter.
Fluid is still pink, smells fresh and the tranny shifts fine.
Of course the best thing you can do is change it every 25k miles from day one which is what I do with my Mustang