For a time I was an avid racquetball player, playing two to three times per week. I always used Penn ultra-blue racquetball balls.
These balls come in a jar that is vacuum sealed, which preserves their 'freshness' which is directly linked to their bounciness. I found that each ball I used was very high in quality. They are easy to serve and the bright blue color makes them easy to keep your eye on as it bounces around the white racquetball court.
I could play for weeks using a single ball. Granted, I'm not a hard-core player and could never hit the ball as hard as I have seen some people hit it so if you play harder the balls might not last as long. But, by the time the label wore off I generally noticed that the ball wasn't going quite as far and would simply get a new one (and gave the old one to the dog).