Kind of a how heavy is my rock question with no specifics.
Load E tires may be a LT225/75-16 at 2680 lbs capacity or a LT305/75-16 tire at 3500-3700 lbs capacity. How much weight the truck/van is carrying when loaded vs when not carrying a load means different pressures. And yes it can means a lot of difference.
Some folks just pump them to the max and replace them in 30k-40k miles.
I air my tires on my trucks to the pressure for the load. I usually run load E truck tires for 70k-80k miles and always change tires just before the wear bars show.
However I know all my vehicles loaded and unloaded axle weights and I have my own compressor so airing up or down is no problem.
Without any specifics on your tire sizes and axle loads just pump them to the max and hope for the best long term service.