2005 GMC 2500 crew cab, 360,000 miles, 6.0 gas 4 x 4, 410 gears, pulling a 27 foot gooseneck. I had replace the engine at 210,000 miles and the transfer case at 355,000 miles. Purchased new.
2004 GMC 3500 crew cab, 451,000 miles, 6.6 diesel, 2 x 4, 373 gears pulling the same 27 foot gooseneck. I had to replace the injectors 2 times. The second time it was done correctly and it was awesome from then on. Purchased used with 69,000 miles. My son totaled it, he was unhurt.
2007 GMC 3500 crew cab, 442,000 miles, 6.6 diesel, 4 x 4, 373 gears pulling a 30 foot gooseneck. The transfer case is being pulled as I write. Purchased used with 109,000 miles.
2002 GMC 3500 extended cab, 236,000 miles, 6.6 diesel, 4 x 4, 373 gears pulling the 30 foot goose neck. Purchased used with 185,000 miles. It is not as strong pulling as the 07 but it gets the job done.
As the above shows I run them for as long as I can. The diesels all have the same cons. 1) The front axles are all wearing the tires. I think most of that has to do with the weight of the gooseneck. 2) The hoses on the hydro-booster leak.
I would never by another new truck for work. I did buy a new 2020 Chevy 1500 2 x 4 crew cab for my bride. I do not care for it. The steering and the brakes are too touchy. She loves it.