FWIW...
All those "zipping along at 70-75 mph"; your ST tires are only speed rated to 65 mph. High heat (hot days or desert climates) and high speeds (excess of speed ratings) are leading contributors to tread separation and catastrophic tire failure. Your trailer being a "come along" behind the driven vehicle is subject to constant vacillations (sway; even if it isn't noticeable, it is there) and those vacillations lead to sidewall flex and heat generation. The faster you go, the faster the vacillations and the sooner the tread gives up and separates.
Just so you know.

I've towed almost 100,000 miles (several trailers) and done it on those "cursed Chinese made tires" and never had a catastrophic tire failure.
Tire longevity and safety:
1) Keep air pressure at maximum as stated on sidewall of tire and check every 3 days or sooner if it looks like one is going down. All tires loose air and after a bit, you'll learn what your tires do. I check mine weekly when on the road; check tires, lube hitch points, check nuts and bolts, check LP level. Every week.
2) Don't overload your trailer. Simple to say, but, especially with toy haulers, not so easy to prevent.
3) Keep your tires covered when not towing. I don't cover mine while on the road, but, when done with the trip, the covers go on.
4) Keep your speed below 65 mph. You'll get better mileage; both mpg and wear on your tires.
Those are the most important...there are other "little things"; try to avoid "sharp" turns (you'd be amazed at the stress a sharp turn puts on tires and suspension) and, of course, pot holes and curbs. The suspension on your trailer doesn't handle pot holes as well as your TV and rubbing a curb frequently is a good way to have the already stressed sidewall start bubbling away from the cordage.
There you are...if you are an "old hand"; just a reminder and if you are a "newbie", things your RV dealer didn't mention when you had your PDI
