A pair is worn out - I'm buying a new pair. Why ruin a good thing? These are reliable slippers that have never let me down. Once you find the right size (for me it's a size up from my usual shoe size, for others it's the same size) you can go back to that slipper and order it again and again, which takes a couple of years. exquisite comfort in each pair. I wear them around the house all day (when I'm home) and I carry them for the occasional trip down the driveway to get the paper or out to the backyard to check on the dogs. And I get five or more years from them. Are there slippers for long periods? No doubt. But none of them were as comfortable or timeless.