Purchased new 2014 Sierra All Terrain with tow package, and now getting transmission replaced at 130,000 miles. Torque converter was replaced under warranty at 76,000 miles. Trans fluids changed @ every 35,000 miles. I tow a few times a month, but trailer with ATV's usually about 2,500 lbs, occasionally I use the larger/heavier trailer (3,300 lbs empty) for a total of @ 5,500 probably 3x a year. Most towing is 100 miles each way to my cabin. I did tow a CJ7 on the heavy trailer back from Texas to Ohio last year.
My YukonX (2500 series) with the 6.2 that I replaced had 192,000 miles, and towed a lot more with it, to include a few times towing a trackhoe for total load of 8,750lbs. Never had a transmission problem.
So, not happy... Should have known, as my neighbor had a 2015 Silverado, almost entirely highway miles, and had to replace tranny at 142,000. He puts @ 50,000 miles on per year, so when that happened, I started to worry and my truck made it another year, then transmission tanked...