This article is from the Pool & Billiards FAQ, by Bob Jewett with numerous contributions by others.
Yes, and not slowly. Within a year of daily play, all the balls
in a set will be smaller than the allowed minimum in the
equipment specs. The cue ball wears fastest, as it is struck by
the tip and skids on the cloth on every shot. It is sent off the
table more often, as well.
Object ball wear comes from friction on the cloth, and is worse
if the cloth is allowed to become dirty. Since billiard chalk is
made of ground up sand, dirty cloth works like fine sand paper.
See item #26 for cloth cleaning suggestions.
As the cue ball becomes smaller than the object balls, it will be
much easier to draw, but harder to follow. Parts of the object
ball design will likely wear faster, so on some balls you can
tell the numbers by feel as the numbers wear faster or slower
than the rest of the ball. Often the "eyes" of old balls will be
found to bulge out.
 
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