When we travelled with a camper on the truck we had two flats on the Dempster Highway and one on the Campbell Highway, both rough gravel. The weight on the truck likely was a factor.
With the fifth wheel, we've had flats on the truck on the Alaska Highway (after driving through a construction zone) and on Highway 97 just north of Prince George.
DH checks the tires every time we stop, which is every couple of hours to stretch the legs. He just walks around looking at everything to ensure things are good. Every morning he checks tire pressure and fluid levels in the truck. Towing long distances with lots of elevation change is heavy duty work for the truck so he keeps a close eye on its status.