I just got back from a weekend trip doing the Three Ridges loop and this was the first time that I got blisters from my boots. I got 1 blister on both heels. This was the 4th trip that I have taken with these boots but this was the first time that I have gotten blisters. I really didn't do anything different concerning my socks or how I tie up my boots. Could old socks, mine are at least ten years old, cause problems. I just don't know what else could cause the blister all of the sudden. By the way, I use liners with my therlo socks. my boots are Vasque, not sure of model. Thanks.