I towed my 1991 boat 1400 miles. I had new tires put on before I left, greased the buddy bearings before and during the trip. On gas stops check your hitch/connections to make sure everything is still tight.
I tow one way 250 miles on average, leaving for 500+ one way this week. Tires should be close if not, at max pressure rating on sidewall. Bearings need to be good. I jack my trailer up before every trip and spin the wheels and wiggle them to see if I am developing any play or funny noises. I consider this a MINIMUM for long trips. I also touch my hubs immediately following any stop to see if they are equally hot. If you have one that you can't touch, then you are developing an issue . . .