Plastic heel taps protect the heels on your boots and heels from getting worn down. A cobbler can hammer taps into your shoes for approximately $3, or you can buy taps online and DIY.
For best results, attach taps before you start wearing down your heels. All the same, you can also put taps on shoes that are already worn down to further lengthen their lives. If you're not handy with a hammer (or are dealing with beloved or expensive shoes), you might want to entrust this task to a cobbler.
Seven-Pair Heel Taps, $10