Welcome to the Pro Shop, where you'll find answers to readers’ most frequently asked equipment questions.

You’ve probably heard that if you wait until you’re thirsty to have a drink, it’s too late—you’re already dehydrated. Well, a similar thing could be said of tennis shoes. But how long it takes a player’s shoes to outlive their usefulness is not an exact science. Unlike a car needing an oil change, shoes don’t obey odometers, as different models have longer or shorter life spans. Lightweight shoes are not as supportive or padded, and tend to wear out more quickly; heavier, more stable, cushioned shoes are often sturdier.

But there are other considerations, including the size of the shoe-wearer—bigger players pass along more abuse to their footwear—frequency and style of play, and the court surface. A serious baseliner hitting the hard courts several days a week will do more damage to his shoes than a casual doubles clay-courter. Depending on how often or aggressively you play, you may need a new pair of shoes as often as every few months, or as infrequently as once a year.

If your shoes don’t squeak anymore on a hard court, or you’re feeling more soreness than usual, it may be a sign that your footwear is wearing out. Another signal that something may be compromised is if your shoes aren’t holding their traction, or if the upper is giving too much while sliding on clay. The shoe’s midsole, which is generally composed of some kind of foam material, will also start to flatten over time with repetitive play, and not absorb shock the way it did when it was new.

Even if you don’t notice deterioration, the general rule of thumb is about 45 to 60 hours before the midsole is worn out. So if you play once a week for an hour, you should be replacing your shoes at least once a year. And if you can’t remember the last time you bought shoes, it’s definitely time for a new pair.