Exactly, that vibration shock is the silent killer. Spindle bearings are meant to handle perfect vertical loads, not get whacked sideways by a fan blade. Each little hit like that makes the preload just a tiny bit off, and you will never see it coming until your finish goes to hell on some critical part. It is not one big failure, but a hundred small ones adding up where the machine just gets a little sloppier each month. The scary part is you would never know until it is too late to just tweak it back.

Seems overblown (but what do I know?)