You can extend the life of your bearings by using lubricant after cleaning the bearing. Use a needle and stick the sharp tip into the oil. Shake it off and touch two of the balls inside the bearing. Any more than this and the bearing will not spin so long and be slightly responsive. If you ad too much lubrication, you will need to clean out the bearing again. Replace the bearing shields and play the bearing in for a couple of minutes after lubricating. See the tutorial at the bottom of the page for how to clean a bearing.