I have been reading about the red line use, 5w 30 I think, correct? I have only used PUP but do change every 5k, may switch to redline after I use up remaining oil.
For the transmission, I have read of problems here or there but without data it is hard to know where the problems are originating. For example if one puts big tires on the truck without upgrades to the transmission, etc. but still launches like a 10 second racer, one tends to have problems. Modifying the truck requires other upgrades or a change in one's driving habits. This is why I don't plan to worry; I will use the truck as it was designed and if I have a transmission failure then I rebuild it with better parts. In my years of driving with near a million miles under the belt I have replaced a transmission, flushed a few, rebuilt or replaced alternators and starters, and replaced a clutch among many fixes. It happens, mechanical things can break.
Could the transmissions have been built to handle more abuse, certainly but at a cost to everyone. I imagine there are millions of these transmissions out there and don't see evidence of millions of failures.