If you get D or E load tires, they'll last longer than LT C or P tires. Air pressure is whatever you want for the load your carrying, roads you're on and how you want the truck to ride.
For day to day empty driving, same pressures as you currently prefer or a shade less due to the tires being slightly stiffer.
After that, it's load pressure table if you're unsure, or run em however stiff you want them. I cannot think of a situation where a full 80 psi is warranted for anything a 1/2 ton can tow or haul, and I can do some stupid stuff with 1/2 tons!