I used Bearing Buddies and would find with the 12" tires that the bearings would need a lot of grease after a 400 mile trip. Started taking a grease gun along for the ride so I could add grease at my destination before making the return trip.
I look at it in terms of what happens if a bearing fails and a trailer loses one of two tires. I was in a car towing a trailer filled with firewood when that happened and within seconds that wood was all across the highway. Luckily the oncoming cars were able to stop in time or it would have been very ugly.
The trailer tongue as badly twisted and needed to be cut off with a torch and replaced. Now I take a conservative approach and use trailers with full size tires and I keep the bearings well greased.