I''ve had 2 or 3 balls that were plugged in de-drilled once.... never went more than 1 plugg n drill..

and 2 of the balls were used from a friend who was going from "storm" to brunswick since he was being "sponser''d" by brunswick... I wish i still had those two old storm balls one was a old El Nino 2000 and a Lighting Flash.

But on the other hand, both balls only had to have the Thumb plugged, to move back like a 1/16th of a inch, and he didnt use grips, so I only had to have the fingers ajusted a lil bit.. So in all reality it was hardly a plug in re-drill.

but i do kick myself for getting rid of those two bowling balls.  
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" Lift Your Skirt Grab Your Balls and Learn How to Bowl "   http://coolluvr4u1976.bowlspace.com/

Edited on 12/19/2009 1:20 PM

As many have mentioned already, I always heard it was about having plugs in your ball track or drilling into the core.  But I've bought many a used ball and don't notice any difference.  These days I look for a ball with a layout I like so I only need to move the thumb and put new finger inserts in it.

I have a Lane #1 Bullet on it's 4th drill and it rolls true.  Somebody plugged it with blue filler (on a dark silvery gray ball).  It's ugly as sin until it hits the pocket