Okay, so it's not as common as it seems, then. I was beginning to worry, because I've seen a lot of posts on it lately in the cat comms, and I was beginning to wonder if I was doing something wrong as a cat mom and somehow not noticing when it needed to be done. (Basically, it's been posted about enough that I was starting to wonder if this was some vital part of cat care I'd managed to miss in the 39 years of living with cats I have).