[Sapientoni]

I was a "predictive maintenance specialist". I received bearing maintenance training from a couple different mfgrs. Roller and ball bearings have a predictable design life time. Bearing size X load X RPM are the pertinent factors that determine "expected" bearing life. Testing has shown that some bearings will outlast the expected life with only a couple drops of initial oil instead of the ounce of grease they are designed for. Others don't make it with all the original design elements. A crankshaft or rod bearing is actually sliding on a bearing made of oil molecules that are absorbing the impacts and resisting the friction. A ball bearing is slightly flexing on the contact surfaces as it rolls. Eventually these surfaces fatigue and pieces pop off. instead of lying back down flat..spalling. Bearing is disintegrating. Repair at safe intervals, be alert to impending warnings, or wait until failure proves you should have replaced it a week ago.
It's a sad day when an "improved design" means you have to spend thousands of dollars to replace a $40 part that used to be replaceable far easier.