One thing that's important to remember is that Toyota has never actually said don't change the fluid. They say "under normal driving, fluid change is not necessary". That's different than "never change it".
If you operate your vehicle under "severe duty" situations...heavy towing, hauling, short-tripping, stop-and-go.....or you've purchased a used vehicle whose service history is tough to determine....then I think it's prudent to service the transmission.
When I bought the Yaris 3 years ago for my daughter the 1st thing I did was change the oil. The 2nd thing....service the transmission.
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