We have 36,000 miles on our trailer tires in the past 3 years and 9 months.
We are on the second set of purchased tires. Replaced the originals at 4,000 miles. Needed higher load rating. Replaced first purchased set at 29,000 miles.
I bought mine from Discount Tire, along with my truck tires. I get more wear on the front tires of the truck because it does more braking action than the rear.
About every three or four months, I stop in and have the truck and trailer tires rotated and balanced. Because it is free and takes less than an hour. I make those stops only when it is easy to do at the start of a towing day.
If I don't put that kind of usage on your TT tires, I wouldn't bother.