[rohrmann]

A bearing needs to be replaced only when there are issues with the particular bearing. There is no replacement schedule, and if maintained regularly, the bearings should be able to outlast your rig. All this is assuming the bearings are quality bearings to start with. The reason some of us have replaced the Chinese bearings in our rigs is because they are much less durable than better quality bearings such as Timken. There are other high quality bearings on the market, too, but Timken seems to be the Go-to bearing we all seem to upgrade to.