That truck has the six speed in it, correct? Not only should he change the fluid and filter, he should add an auxiliary trans cooler if it doesn't already have one.
My 2009 Suburban has had the fluid and filter changed at 9,000 miles (when I bought it), 50,000 miles and 100,000 miles. At around 125,000 miles, I found the fluid was brown and burned. I had the trans shop flush and service. Last month, at 139,000 miles, it wasw slightly burnt again. Shop flushed, serviced and added a factory cooler. Inside of the trans looked ok.
With the cooler, as small as it is, the trans temps are nice and low, like 174 degrees at 70 mph on a 78 degree day. Fluid seems to be lasting fine. We'll see as I rack up some miles.
I'd like to hold off on a rebuild if I can as it costs about 3500 dollars.
Also, tell him to drive that truck around in M5 and not D. It keeps the engine in V8 mode and not that stupid four cylinder thing that fails and destroys the cam. I drive mine in M5 all the time and it runs great.
My brother's 2007 Tahoe had one of those controlled intake lifters fail. It destroyed the cam. You have to remove the heads to change lifters in that engine so we swapped the entire engine. We replaced the four DOD lifters with regular intake lifters and he had the system programmed out of the computer. Truck has been stellar ever since. He drives it every day as it's his work/ family vehicle.