No break-in time - wore them the first day for try-on (walked around the house) and then wore them to work the next day. Totally comfortable. I have "normal" calves, meaning they are not thin and I usually have issues with boots zipping up to the top. These had enough stretch that they zipped up all the way after about 5 minutes of wear! YAY! They are really cute too - stylish (I'm 53) without looking desperate. Not going to be able to wear them outside of my jeans, which is ok, I don't usually do that! The lining isn't exactly warm, since it's not down in the foot area, but they are very much appreciated at the top of the calf (in the front only).
Another winner.