The trailers just 3 years old so not about to replaced anytime soon , we don’t really do many miles probably about 70,000 km a year but yea the trailer tyres do ware out pretty quickly although the rear axle does lift so that helps a bit .
The main issue I have is with this particular tyre company is they pay there fitters partly on commission so the more they fit the more ££ they make 
( The one lad said they get 30% of the profit made on each tyre )
Previously I had a trailer tyre needed changed because of side wall damage on the outer one ,the matched pair were only a month old 
this particular fitter changed the inner one as well 
I didn’t challenge him about it at the time , but just proves what a bunch of ■■■■■ that firm is 