a few hundred thousand mile towing things, I personally use radial tires mostly,(due to better ride and they tend to have less vibrations and balance better)
but I ONLY use tires rated for loads higher than I need and I ALWAYS make sure I check speed ratings and get highest I can also in same load rated tire!
smaller tires turn a LOT more often than larger tow vehicle tires, so speed ratings should be higher if your a driver that tends to inch past speed limits a alittle!!
as load ratings again,
if a C will do, I go D or higher!
Rather a tougher tire than a lesser one when on trailers
and I also replace them based on TIME that passes and NOT how they look or how much tread is left (this is also why every tire made has a date on them)
for me, its every 5-6 yrs and I go new if NOT sooner, pending use and miles and well, where I will be towing to!
I have had a few blow outs over the yrs and if I can prevent another one, I will, much cheaper to replace tires sooner, than an accident and down time and risks of changing them road side IMO! niot to mention the stress you will save yourself from a blow out!