I used Sorel insulated and waterproof boots for winter stargazing sessions. The rubber of the boots themselves has perished, but the felt liners are in good shape. I only ever stood about in them in the garden. They weren't used for distance walking/hiking. These liners could be what you need to rejuvenate your own boots. I've included a photo of one of the rubber outers so you can see the style these liners fitted.
