Well, my lady had a Pontiac Sunfire that went 214,500 miles and never had transmission fluid changed. It always did great and had zero issues and we sold it with that mileage still doing fine. My Nissan Sentra was a 95. I got it when it already had 118,000 miles. I drove it to 242,000 miles, changed the motor oil every 4k miles with Castrol Syntec. I never changed the transmission fluyd. Guess what gave out in the Wendy's drive thru ?? The motor. A friend of mine had his own junkyard. I gave it too him because three different places I took it said it was done. I bet the timing chain broke. Which my friend said was the case. He put a motor he had in the yard on it and it was good to go.
So, I maintained the motor very very well. Never changed the transmission fluid. And the motor went out. So, my experience has been that the transmission fluid in cars is really not all that big a deal. Sorry but just the case with ALL of my cars I have ever had. Ones prior to the two mentioned has well. My opinion is that the transmission is a sealed case not exposed to contaminants like motor oil so it is not necessary to change it very often. Heat is certainly a factor. But with these newer cars using synthetics I would think that would mitigate any troubles there with most cars or trucks. If you decide to change it.. I would change only about half of it. All new fluid may well lead to slipping if 100% new fluid is put in. And DO not flush transmission. This will definitely lead to failure.