I think the owner's manual for the Ram 1500 recommends 100,000 mile service intervals for the transmission. Vern has an estimated 750,000 miles on his factory transmission. He sticks to the 90,000 - 100,000 mile trany fluid intervals.My 2019 RAM 3500 called for a transmission fluid change at 30k miles, towing or not. That seemed remarkably soon for an HD trans designed for towing.
I don't log that many miles, so I'll stick with 5 year/50,000 mile intervals, whichever comes first.