The brain has now been shown to be a 'plastic' organ, it can reorganise itself throughout life. Hence the healing can continue for as many years. You will need to train yourself for this, you should continue to expect further improvement as long as you continue to exercise your brain, by doing mental exercises like jigsaw puzzles, crosswords, etc. Yo can also take up learning a new skill, like learning to play some musical instrument. All these have been shown to have a great 'exercising' effect on the brain and helps in improving its function.