A good aftermarket bearing/hub assembly will have no problems. Timken, SKF, etc. have heard no problems with. I have two Timken's on the front of my car with no issues. I have heard about but never seen an issue with some of the less expensive options (read Chinese imports) however, I can tell you that I know of a lot of shops that use them in many other brands of cars with no issues or any worse failure rate.
Did you install the bearing/hub assembly yourself? If so, did you make sure and tighten the ABS sensor back into the knuckle after you put it in or was there crap on the end of the sensor? I've seen that happen before because it's a magnet. You might try removing the sensor from the knuckle (if it's tight now) and cleaning the end of it off really well and see if that helps.