I think the main issue with ST tires is the 65 mph max. rating they have, and not so much the safety related to the posted max. speed or the gas mileage.
So many shocking things you see other owners doing related to tires. Not just blowing by you on the interstate, but grossly overloaded tow vehicles everywhere you look. I try not to look anymore or think about it when I see them. Downright scary sometimes. I just try and focus on what we've got and doing it right. Sadly, it's hard to learn about this stuff unless you go to forums like this. It's like going to a doctor who will write you a prescription for whatever you want. RV dealers and manufacturers, tire makers, etc. will give you whatever you ask for. They just don't tell you what the side effects and signs and symptoms are of using over capacities.
The biggest thing I am getting from various posts is that the basic ST tires that most trailers have, are simply running at the max. of their capability at 65 mph and that running consistently at 65 and/or too often at over 65 mph is bad, bad, bad for these tires. Then they don't seem to be able to handle much abuse at all like running up against curbs, and running over or under inflated, extended exposure to UV rays and heat, hitting bumps and potholes and running them close to their max. load capacity.
For maximum ST tire life and satisfaction, it seems like they need to get the treatment and respect they need, not deserve. You've essentially got to baby them.
We are going to upgrade to Marathon tires, simply because that's all we can with our dealer without incurring a major expense. Interestingly, I asked our dealer why anyone would upgrade to Marathon and he had no idea!! Are you kidding me?? Maybe not tho because they routinely sell trailers too big for your TV.....