I don't know why everyone on the forum seems to recommend running at the maximum specified pressure indicated on the tire. The tire manufacturers themselves do not recommend that. Instead, they give a chart that shows the proper inflation depending on the amount of load the tire carries.
On some tire manufacturer sites, they tell you that serious over-inflation will make the tires less flexible and more prone to damage when hitting rocks or potholes or other road hazards. Tires also provide some cushioning of the load and if over-inflated, your trailer is subjected to a lot harsher shaking on gravel or uneven roads. Aside from scrambling the contents of your cabinets, that can also loosen up joints throughout the trailer.
My approach to the tire problem was to buy what folks consider to be really good tires (Maxxus ST Radial 8008) and of a capacity greater than the original equipment (load range D/8 ply rating, instead of load range C/6 ply rating). Then I looked at the Maxxus pressure table and determined that with a generous estimate of my loaded trailer weight, each of the 4 tires only needed to be inflated to about 34 psi. The maximum inflation of these tires is 65 psi.
I confess I just could not do that. I've always inflated vehicle tires a bit more than the manufacturer recommendations. So I settled on 45 psi. According to the chart, that's adequate for a trailer weighing almost half again what my Hi-Lo does. Still, that's a long way from the 65 psi maximum, which would handle a trailer almost twice as heavy. I feel like I've made a decent compromise.
The other thing I do is treat my tires decently on the highway. I drive a maximun of 60-65 mph even on the freeway, which here in Idaho now has an 80 mph speed limit. I'm a lot more comfortable with that speed too; even with the Hi-Lo's electric brakes the stopping distance is going to be a lot greater than without the trailer, etc. And after all, most trailer-specific tires are only rated for up to 65 mph.
I do see plenty of folks towing their trailers and huge 5th-wheels on the freeway at 80. Of course, that causes a lot more heat build up in the tire sidewalls, which is the cause of most tire failure. I think a lot of folks just put the maximum pressure into their tires so the sidewalls flex less, especially on hot summer days. They reason they can tow at what I think are unsafe speeds with whatever tires they have.
I'm sure not everyone will agree with this, but I thought another opinion might just be something to consider.
Roger