Pick up any can of tennis balls and you already know how this story ends. That crisp psst when you crack the seal is the sound of a countdown starting. Within a few sessions — sometimes a single hard afternoon on a hard court — a lively new ball goes soft, dull, and forgettable. For the everyday consumer, the club pro, the school athletic director, and the sharp-eyed entrepreneur, this isn't a minor annoyance. It's a recurring cost line and, if you look closely, a genuine mar