Buy cheap, buy often.
I've had neither good or bad things to say about tires, usually they crack and dryrot before any problems arise. Same for the wheels, they rust or leak.
It's just been a habit to replace the tires about every 2-3 years on the trailer being taken on long trips. Now the local ones, that is a different story, usually they get the leftovers from the roadtrip trailers.
Normally I buy the tires and wheels at places like Agri Supply, Tractor Supply, etc.
Biggest problem I've seen is the idiots that won't read the inflation recommendations on the tire. Had one idiot that followed us to central Fla, had a blowout and said "don't know what's wrong with them new tires, I put 35psi in them before leaving the house" (yes they were supposed to have 50lbs in them).