Tow vehicle tire pressure

I don't have a dually, but have always run the pressure where I felt it was best. I put LT load range D tires on my 1/2 ton. Those have a max pressure of 65 PSI, but I never went that high as they were overkill for the truck/application. For heavy loads or towing the trailer, I'd run 60PSI. For everyday driving I'd usually run about 45-50 PSI. The tire company, Les Schwab, that installed them recommended lowering the pressure for everyday driving too and would set them at 40-42 when I went in....I liked it a little more than that. When I inquired about the recommendation of running max pressure, they said no, alter it to fit the load. I did find if I ran high inflation without a load for too long I'd get excessive wear int he middle of the tread. It was nice to have the excess load rating there when I needed it, but nice to air down the tires to soften things up a bit the not. I got 85K miles out of those tires....siped when installed.
I now have a 3/4 ton diesel with load range E. I run 60psi around town and air up to 70 with the trailer/load. Not enough time on them to determine if that's the right fit yet.