The photo's by psychpw, clearly shows the reason why a "major brake" job should be done every 10,000 miles or once a year, which ever is first.
Water can and does get into the bearings. The only way you know for sure, is to pull the hubs.
Just because a trailer may not have moved for a year, does not eliminate the need, for a major brake, or at the absolute minimum, an inspection of the spindles and bearings.
Usually, if the spindle is rusted, there may also be some rust on one or more of the rollers in the bearings.
Bearing and brake condition should be number one on everyones PM list.