Axle brake inspections and re-greasing is minimum 1 x per year or 12,000 miles (which ever comes first). Since this Trailer hasn't been re-lubricated since last 7 years, I would simply do all 4 hubs NOW.
For details, surf:
- click here - To learn how to perform brake inspections and axle re-greasing yourself, surf:
- click here - You-Tube has lots of videos on brakes inspections and wheel bearing re-greasing as well. Very easy DIY job. Especially if one wants to save lots of mandatory maintenance dollars.