[steamer]

If I got the right machine as yours from Grizzly the main spindle bearings are 6206-2RS. The 2RS means the bearings are sealed for life and don't require any more grease. I too have had problems with off shore bearings and they tend to be noisy. One thing to watch for is side load! if you had the spindle apart when you got the machine, you may have put some on when you put it back together without knowing it. Tapered rollers need preload when going together but not ball bearing. The reason ball bearings don't last long in a mill is, if your milling it's a top load on the bearing but drilling is a side load and that wears them out quicker.
Rob