I have never have had to replace one, I always take the hose off and drain it before it gets below freezing. I have 3 on my house. The valve is actually back inside the basement/crawl space, I could see if the wall hydrant isn't level or slightly down hill it might not drain and freeze.
https://www.menards.com/main/plumbin...104498&ipos=73
Some people put insulated covers over them but I've never. I don't have shutoff valve for them either.