Trailer tires are crap. I've replaced all four of mine in the three years it's been on the road. The last time my tire guy said he ordered 6 of them in before he found one that he thought would mount round on a wheel. Thought they were crushed in a container. i use the heavy duty Carlysle sport tracs. Doing it again I would get Goodyear marathons.
I had to move the front support, winch stand, shorten the bunks and re-carpet them, rebuild all the lights, weld up the main beams, replace the fender mount brackets, and replace the brakes. This is on a 2006 aluminum trailer. Oh, and tie-down bought me a new master cylinder.
Now the springs are looking pretty rusty, thinking about replacing them.
My boat motor and trailer get freshwater flushed after every trip.