Heat kills transmissions, so coolers and 50k service intervals can make the difference between no problems and replacement.
Keep the selector in the "lower" drive position in town to help prevent gear hunting, which creates more work for the trans. Even transmissions prone to failure, like the late 1990s/early 2000s Chevys, can be made dependable with the addition of a shift kit that ends those nice smooth shifts but prevents gear hunting.
Remember three-speed autos? Pretty bulletproof. Add overdrive fourth and more problems pop up. New transmissions are pedestrian if they only have six ratios, so I wonder if failure will be a bigger problem in the future.
PS: Need to buy a new truck to avoid repairs? If the only repair you have between 100 and 150k is a $2,500 transmission replacement, you're money ahead.
The only financial reason to replace a truck rather than continue to repair it is the cost of unplanned downtime, which can be a business killer but is easily handled with backup equipment. (Excluding wrecks or terrorists getting into Rico's
compound.) We buy new trucks to avoid downtime, but also to make techs feel like they're being rewarded for providing great service. You don't have to apologize for WANTING a new truck, or feeling better once you get it, but it's an emotional decision not a logical one.