The average bowling ball is 8.585 inches in diameter. The minimum allowable size by USBC is 8.500. Using the most common pad of 2000 grit. You would have to bowl 650 plus games using the recommended technique before your ball would be in danger of becoming illegal. Sanding your ball to maintain the surface is safe for consistent use.
I copy/pasta the above from a blog post on surface changes:
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