How much weight are you talking on the utility trailer?
The trailer weighs 700 empty, it has a 3500lb rating. The tires are 17 years old (F78-14's) and have been absolutely trouble free.... I have only used it locally the last few years, but with a trip to CO coming up I want new skins on it!
Mine is a homemade jobby, 550lbs empty, and I've been running cheap "used" tires on it exclusively (all car as far as I can remember), simply because the thing sits 99% of the year, the car tires are rated for 12 or 1500lbs each, and I've got a spare. I just can't justify buying new tires for something that might get 1500 miles a year. My load (I call the trailer "Exxon Valdez II"...propane, gas and diesel) has been 1540lbs the last few years, so 2090lbs. This year I'll be bumping it up to ~2800lbs. I'm more worried about the old axle than I am the tires, but it could be a learning lesson lol.
I've not had any issues using the car tires. Only one I've destroyed was because it was too wide and under load rubbed a spot on the frame and took out the sidewall. It sees logging roads with nice potholes, loaded. I try to take it easy, but it still bounces around a lot.
The 8 year replacement is not a joke on tires. I'd rather run a nearly bald tire on a trailer (or vehicle) that is two years old, than one that has full tread but is 9 years old. My BFG's started to slowly leak around 9 years (through the tread area, not the bead), and I had trailer tires that started to slow leak after they were well past their prime as well.
It's getting harder and harder to buy non-chinese tires.