I'd like to offer a counterpoint: quite likely you'll reach a ceiling unless you move as a kid or, better yet, as a toddler or baby! I spent ten years in the US, and was very lucky to have a wonderful native uncle who cared a lot and, sometimes tenderly and other times quite bluntly, corrected me constantly, but naturally this became less frequent.

I was 17 years old when I arrived in the US, and after half a year there I could almost sense getting better by the day, it was an extremely exciting experience. My very naive illusion, however, was that this progress would stay linear until I caught up with the natives, but it unsurprisingly plateaued, in particular when it came to my accent and pronunciation. But again, that first half year felt amazing!