All balls lose reaction over time, some become merely smoother, milder, essentially urethane balls, some actually become totally dead. Even most standard urethane balls will "track out" if used for too many games without a resurface. Some balls can be largely brought back to life with an effective cleaning and resurfacing. Other balls....well, Voodoo incantations and the height of technology can't revive them.
What really happens is that balls lose their "reaction" -- i.e., the hard turn at the end that marks aggressive balls. This loss in reaction is less noticeable if you: (a) are relatively heavy handed and (b) prefer equipment that arcs. Frankly, I can hook the lane with plastic balls on many top hats, so if you are on an ordinary house top hat, you won't notice the loss of reaction as much as you might on a more uniform oil pattern.
Finally, the loss of reaction seems to vary from coverstock to coverstock and indeed from ball to ball. Some Brunswick coverstocks seem to have greater shelf life than most other coverstocks. Dynothane's new "soaker" coverstock seems essentially indestructable so long as you keep it relatively clean and resurface it after a reasonable number of games (around every 150). So all balls die and most pretty severely, after a number of games -- even the manufacturers admit it.
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"I don't mind if you don't like my manners. I don't like them myself. They're pretty bad. I grieve over them on long winter evenings."
