If you have a heavy 5er with E rated tires I'd recommend replacing them soon with G's
On my commercial trailers and my rv trailers with 5.2k-6k axles/16" wheels I use and recommend LT E such as a Bridgestone R-238/others. Their good for 50k-60k miles and no issues.
One poster says his ST cheapie tires are 15 years old...this tells us he travels very few miles per year.
Lots of rv trailer owners don't run but 3k-6k miles per year vs those of us who travel 7k-10k miles per year. ST C/D/E simply won't hold up to that type of use.
I would recommend a quality commercial grade all steel ply carcass load G ST235/80-16 tire at 4080 lbs for 7k axles.
Or the same tire in a ST235/85-16 at 4408 lbs capacity on 8k axles.
I wouldn't recommended over tiring any highway trailer above 15-18 percent above axle ratings.