You are correct. This subject has been discussed before. My opinion has always been and it's based on 35 years of teaching and working on cars. Bearings do not have to be greased as often as the trailer manufacturers require. It is my belief that they recommend annual or 12,000 mile intervals based on boat trailers which are immersed in water periodically. Also some units don't get much usage over the years. They are moved from point A to B and set most of the time while others are moved much more often. So to cover themselves they recommend more frequent intervals than I think is necessary. That has opened up this can of worms. Many have adopted an easier way of lubricating the bearings with less work. Using a grease fitting with a hole drilled into the axle or the never lube system. This has created another problem of excessive lubrication. Some people think if one squirt is good 2,3, or more is better. Either of these systems may work well but you open yourself up to extra steps that may or may not be followed correctly. EXAMPLE: If you grease your own bearings using the zerk fitting do you raise the wheel off the ground and rotate the wheel slowly as the grease is pumped in??? It is warm enough so the grease will flow easily??? Have you switched lubricants and is the new one compatable with the old??? Was the original seal installed correctly so that grease is not leaking out and getting onto the linings???? There are lots of things that can go wrong when you add steps to the process.
All of this extra maintenance and lubrication is predicated on the belief that TT bearings need lubrication every year or every 12,000 miles. Front wheel bearings on trucks only require repacking about every 35,000 to 40,000 miles. Why are trailers different????
Here's my approach. Before we take out first trip I will replace all wheel bearings and seals with some better quality parts (non China brands). I don't believe their quality of steel and QC is up to some others. I've discussed this with others and will look for better parts when we get our new trailer. I will pack the bearings with either Mobil 1 or Amzoil synthetic bearing lub. Then correctly adjust the bearings (.002 to .003) side to side movement of tire. From the initial work I will inspect and repack bearings every 2-3 years.
Beyond the tires the next weakest link on the TT's are the bearings. I have read many horror stories concerning bearings burning up, loosing wheels, greased linings etc. within the first year after delivery. I know the units are towed from the factory to the dealers so they have to be set up reasonably well but then why the failure. I'm leaving nothing to chance. My unit will be inspected and all installation problems will be corrected before I leave town.
Just my opinion and I'm offering it to help others avoid these extra costs because of poor or excessive maintenance.
TeJay