beeker said:
My steering seems fine (though those who have ridden behind me may disagree).
My experience is the same as Vinny's: miles of road thrashing eventually causing notching and a couple of broken races.
The wear was slow enough that I never noticed any symptoms when riding. One day I put it on the center stand and jacked up the front end. Turning the forks side to side there was just enough drag that they stayed in any position I left them in though they did turn with only slight pressure from one finger. At 'straight ahead' there was a definite notch. By comparison it almost felt like a clunk.
New bearings (uncaged ball) and races (that was fun) later: no notch. The forks turn easily with one finger and would only stay still when straight ahead give or take. Turned to the left or right they would fall to the stop. The steering definitely felt smoother and lighter. I'm not nearly rider enough to notice the onset of wear. It was by chance I noticed the problem and by the sudden contrast felt the improvement. It seemed fine before but was much better after.
Keeping the bearings properly adjusted as they wear would probably help prevent wear. Having more compliant suspension for the rider might do so too. Roller bearing instead of ball bearings too. Many riders state rollers increase handling performance. This may be just new bearings in general and reduced wear long term.
For the efficiency of the lights I'd agree with grounding them to the frame or even to the battery (via fuse box or relay connection if available or need be) but seriously doubt oil is a factor to be considered at all especially if the lights are LEDs.