I've had transmission minor transmission issues with my last two trucks ('15 Silverado 6 speed and '17 Silverado 8 speed) at about 70,000 miles. I don't consider myself to be in the severe category, but when I changed the transmission and transfer case fluids they were pretty rough looking. It fixed the issue both times. Maybe I do drive a little more severe than I thought. I've realized that tighter intervals (I.e. severe schedule) are needed for my driving habits. I just got the 2021 Sierra AT4 6.2. Too much money not to do the maintenance!