When you buy a pair of hiking boots, they are usually pretty well broken in right out of the box. The leather will be soft and supple, and they'll have a little cushioning. You might feel some resistance when walking in them, but nothing too difficult. If you have an older pair of boots that's been sitting around for a while, or if you've had them for a long time and they aren't quite as comfortable as they used to be, it's time to give them some more wear.