Yeah, mine never really went away either, I was huge for ages between about 3months - 18months, then the went down a cup or 2. (Depending on brand)
Oh, hang on, when I finished feeding I was pregnant, but she was only having one feed a day. Not sure if it counts lol But they haven't gotten any bigger at all this time around feeding DD2, which I think is odd. And they didn't get any smaller or bigger when DD1 finished feeding.