[BrianG]

Are you talking about the pillow ball unscrewing from the A-arm, or the pillow ball cap loosening?

I have never had major problems with either of these. I usually checked the pillow ball cap once every several days of running and maybe one would need slight adjustment to be perfect.

Since then, I started using the RPM axle carriers (kept breaking the stock ones) and seem to be tightening them more often, but nowhere near once per pack.

It sounds like the grub screw idea that BP-Revo suggested might work well for this.