I took my 2015 in for the 32,000km service a few months ago.
Brakes were at a pad thickness of 9/11mm on all four wheels. I was told that this was very good. He said at this mileage most Tundras are at around 6/11. I think he had said you have to think about replacing around 2/11, but I may be incorrect on that one.
I tow somewhat often, but trailer has electric brakes, so I don't imagine the towing wears on the brakes at all. I tend to stop with plenty of time - never tailgate or slam on the brakes hard (unless I need to: deer, cars, kids, etc). Also go up the mountain 5 or 6 times a year, but most of our driving is city, lots of stop and go, so pretty happy with minimal brake wear.