My experience is that it should have plenty of life left, of course if you are just looking for a reason to purchase a new truck you could consider it over the hill so to speak and go shopping. Every GMC, Chevy, or Cadillac we have ever owned has easily delivered great service beyond 150K miles.
Just a few weeks ago our older full size Chevy Express conversion van with the same engine as your truck and 164K miles, transported 6 adults and loads of luggage through Phoenix and Vegas, 110 degree temps, heavy traffic, and she purred on like she just rolled off the assembly line. Typical of all our GMs.
Same thing goes for our Silverado HD tow vehicle, it is a bit older than your truck with about the same mileage as it is a dedicated tow rig, I sometimes think of going new, but what for as it easily handles our 10K# TT. Plus it has been paid off for nearly a decade, no need for new unless I go to larger RV.