I got 170,000 miles on my 93 aspencade pulled a Kwik Kamp trailer probable 30,000 miles. I had to replace the rear wheel bearing a few years ago, with about 120,000 miles on the bike at the time. Can't say for sure that pulling the trail was the cause or not.
Some folks just load them way to heavy.
From the Northwest Corner
Tyrre wear is likely the most noticeable thing when pulling a trailer often. Increase in friction/drag that kind of thing. Regular preventative maintenance should pretty much cover most other things barring unforseen issues, and that's just something that happens to unlucky souls. Thorough visual inspection (regular, like before each day or long ride) can detect most of the clues to wear and tear.