Curious. I hear and see discussions about how a ball's surface is adjusted within a small amount of time throwing it on the lane. Is this true of older bowling equipment? Would an old Urethane (or Old Reactive, 20 years ago) ball's surface change just a fast?

All depends on the covers, there's no absolute. The harder the material, the longer it's going to resist changing via the lanes. So age, by itself, isn't a determining factor as much as cover malleability is. Now, of course older equipment tended to be harder materials so if you want to look at it like that then yes it may carry some weight, but the age by itself doesn't make a cover more durable.

Actually, resin is urethane with a resin enhancement.  As to the original question, pure urethane ( pre 1991 ) equipment absorbed more oil than we thought, and degraded as a result of oil absorption and surface wear.  The normal practice in the urethane era was to create friction by sanding.  Surfaces as low as 400 grit from the factory were common.  What usually happened is that the extremely rough surface absorbed oil, and polished up to the lane.  As a result the most aggressive urethanes lost their reaction pretty quickly.  Our only option back then was to rough them back up, but it was not totally effective since the shell had still absorbed oil.