Few yrs ago we were camped at a project and I checked the tire sticker on every 5th wheel and TT in the group. 1/3 specified ST tires, 1/3 specified LT tires and 1/3 only specified tire size (which by the sizes implied ST). Anyway, generally those that specified LT tires were newer, heavier (and more expensive) units like DRV, etc. while those specifying STs were lighter and/or older units.
My take is that if these heavy, expensive units can run LTs and presumably have good results, then there is nothing wrong with LTs on any unit. Especially since there doesn't seem to be different leaf springs, wheel bearings, drums, etc specified for use with LTs vs. STs. I'm happy I made the change 4 yrs ago. By comparison my previous fifth wheel with STs had catastrophic failures a 3-1/2 yrs and those were one of the best ST tires, Maxxis.