<<Since many of the bearings used in machinery are not 'common' ones used in the automotive industry... >>
Again, I must respectfully disagree. Many of the bearing we find in our woodworking machines are used as bearings in automobiles and other equipment. What might be an arbor bearing in my Unisaw could be a power steering pump bearing in your Chevy (In fact, I got new arbor bearings for my Unisaw at an auto parts store and they were bearings used in many automotive applications - the clerk knew the bearing number as soon as she saw them). Alternators, A/C compressors, clutch pilot bearings, starters, etc., all often use common bearings that can often be found on lots of industrial equipment.
When engineers design a new part, they avoid having to use proprietary bearings to reduce cost. Because of that we have standardized bearings that are used in many industries.
You said that automotive bearings <<..are mostly tapered roller bearings, not deep groove radials..>> Automobiles use tapered roller bearing for wheel bearings, axles, etc, but you are forgetting all the other accessory applications. Also, if you are worried about shelf life, how long do you think the bearings from a woodworking machine supply company have been sitting on the shelf? I don't know either. I do know that my local auto parts store is a busy one and has a pretty good turnover on their parts.
One thing to be cautious about when buying bearings for woodworking is the type of seal or shielding that's used. Metal shields can let fine dust through. Stick with bearings that have rubber or plastic seals.
Bill