Think it's an alignment problem. Bent axle, bent or damaged forks or maybe just one of them so they don't work together but flex in the bearing pockets.

It especially bothers me that the problem appears to be progressive ie you made it a year and then you made it 300 miles.

I would disassemble the front end down to the triples.

Check each fork leg for smooth and even operation.

Loosely reassemble everything. It should slide together like a fine shotgun or camera. While it's still loose shake it. This will help it self align. Then start tightening everything up to factory settings.

I've done this a couple times and I started at the axle-keepers and moved up the forks from there.

You might have also bent a wheel but this would show in braking - especially obvious shaking.

Good luck!

 

A: front or rear?
B how? what tool did you use to install them?
C what nuhawk said,, may simply be an alignment issue.

 

There are only two reasons that would cause a new wheel bearing to fail that quickly.

The bearing or bearings are not in straight. ( which should make axle installation difficult )
This happens when a bearing is driven in crooked and shaves aluminum off the bearing seat which ends up underneath the bearing, misaligning it.
This leads to side loads a radial ball bearing was never designed for.

Or:
The center spacer was left out, this will also cause a side load issue.
This should show itself when you tighten the axle nut and the wheel becomes hard to turn.

Look at Ref. # 6 in the attached illustration. That is the bearing spacer that keeps the inner race aligned with the outer race when the axle is torqued down.

Kai Ju