Although it's not in writing, VCNA service reps and instructors tell dealer techs and service writers that the fluid should be changed and a simple drain and fill still leaves many old quarts of ATF in the trans SO a flush is best.
The term "life" of any car part is going to be determined by several things BUT the only thing that ANY car manufacturer cares about is getting any part past warranty. They don't care what happens after that and they'd really prefer that you just trade the car in and buy another new car. That's how they make money.