About 2 years ago I took my trailer to the tire dealer I deal with and they agreed to pull the wheels and check the wheel bearings as it had been about 5 years since being check. I told them just to put new ones in, but after pulling and cleaning, he showed them to me and said there was nothing wrong with any of them so he greased them and put them back on. I told him that I had been reading about needing to repack at least every two years or so and he said that was a crock of bull droppings. He said I was wise to check them every 5 years or so depending on mileage and usage (very dirty roads, etc) so I am going by that now.