Need to watch the cost of bearings, they are 62mm OD Barden for replacement 2 pairs angular contact, under Moore special modified pre load, that is 2 times standard heavy pre load for the nose pair.
The Bearings begin to get warm or hot when at the end of their shorter then normal life. The Quill should stay pretty cool running full speed for 20 minutes extended. If the quill gets to warm, it wont retract into the tight fit spindle housing.
Bearing replacement, requires the actual load in pounds be applied to each bearing inner race and the deflection measured, and then the bearings spacers ground to length for the custom pre load.