PartyMarty,
Leave your 265's at 80 psi and your tires will last even many more miles than you have seen. All our vehicle's tires are always kept at max inflation as there's so much less sidewall flexing, cornering squirm, and a lot less tread friction on the road's surface. Flexing rolling squirm, and friction create heat and fatigue which is what destroys/compromises a tire's carcass structure and the rubber compounds. Your GM 2500 truck will still ride very comfortable and handle excellent at 80 psi however some other HD brands of pickups will ride like unsprung buckboards unloaded at 80 psi.