I always get a chuckle when looking at used trucks on car lots, the sales people run real low pressure so the used vehicle rides like a Cadillac, but anyone who really works a truck knows that isn't safe nor economical.
As a professional driver I can tell you never let air out because of temperature. Big rigs run coast to coast, sea level to 8000', deserts to Alaska, and you never see truck drivers adjusting their tires. Cold check first thing in the morning before you roll and visual inspections the rest of the day.
During braking it's a known fact that the front tires do much more of the work than the rears, so a slightly lower pressure will provide better traction, but that has to be balanced with your load requirements. A heavy camper (such as mine) will exert a tremendous amount of extra load to the front axle during a panic brake and I want my front tires to hold up to what ever is required to get out of the situation in control.
Personally, I run 65 up front when empty, always 80 in the rear and then air up to 80 in front when I have my camper on. And if you travel the Interstate and you see a highway scale house is "closed" to commercial trucks, you know you can always drive over the scale and weigh your truck just so you know where you are at. Most times the scales are left on and you can read the numbers in the window or on a sign in front of the scales. Hans