The thing dougrainer is right about, is that many new trailers do not come with the bearings adequately greased, and yes, most likely cheapest grease. If no early maintenance (further greasing) is done, failure could happen within a year or less.
I've purchased a number of new trailers, not all RVs. I check to see if the bearings are well greased. I only remember one that was. If the trailer has EZ-lube hubs, I use the proper procedure to pump good quality new grease through, until it comes out the front. Unless I notice a problem with brakes or hot bearing, I am good for several years.
My current FW in sig had very little grease on the bearings, when purchased new. It was easy to see that the EZs were not used, and looked like a finger tip of grease wiped on bearings.
I am sure that fj12ryder has done the same with his TH, as I have with mine. He has not just towed it for 5 years, and not looked, or added good grease as needed.
Jerry