This may or may not be an issue, but I just bought two National (Federal Mogul) rear wheel bearings (Part # 513056) for my Brat from ADAP.  The packages appear like they have been sitting around for 20+ years, totally worn, beaten up and dirty packages.  The bearings within appear fine and are genuine NTN units from Japan, but certainly NOS.  Should I have expected to receive fresh units?  Any improvement to these over the years?

As long as the parts are in good condition, the appearance of the package is no issue. I've bought a few things from one of the local parts stores that's been in business for a few decades. Packages were like you described, but parts were good.

 

There are 2 different types of rear bearings for the 4WD EA81/EA82 rear, has to do with total number of components. But they are fully interchangeable, so don't fret over that difference.

Here are a couple of pictures.  Bearings appear fine.  I cannot complain as they cost ~$30 each.  I do not need to replace these as yet.  However, I noticed my rear CV boots appearing to be fatigued and with cracks on the rubber.  Before those give away, I want to redo the CV boots.  At that time might also do the bearings.

Edited November 3, 201312 yr by aba4430

I would start spraying the rear axles down with some PB Blaster now, and continue doing so for a bit, can't really say how long. But I would spray them every other day or so, just to get some of it soaking in.

 

Rear axles tend to seize to the stubs on both the rear diff and at the trailing arm.

 

I would also spray some on the bearing retainer nut on the trailing arm.