Originally Posted by Master Yodub
Well you don't technically need to replace them, but it's a good idea. Just make sure they are clean and don't get any kind of dirt/sand/debris on them when reassembling the motor.
The biggest thing I worried about was whether the bearings were on there correctly, so I didn't spin a bearing on startup. Everything was good though. I would have replaced the bearings if I either had more time or they needed replacing. They were all good and tight, so I didn't bother.