G'day adclark; I run 40-42 psi for highway driving. My D4 with all the aftermarket gear fitted & two full tanks (192 liters) & two of us onboard with average baggage/gear etc ,is
at the max gross vehicle mass of 3240kgs, so tire pressures are very important to keep moving in very rough stuff.
I'm happy to air-down to mid-20's on rough gravel/dirt tracks when needed, but usually don't bother as the KO2's are very tough. It saves time using the compressor if only
driving a relatively short distance in the rough. With the 265/60's I'm happy to go down to
18-20psi for sand driving & 22-24 on very rocky terrain - better traction & easier on the tires. I've seen many tires off the rim at 14-16psi in sand or mud, especially when changing direction quickly, so I'm very wary of going below 18psi.