Research has shown that building top expertise in any skill is a result of long and repeated deliberate practice time. Deliberate practice consists of four elements:
1) It is designed specifically to improve performance.
2) It is repeated a lot.
3) Feedback on results is continuously available.
4) It is highly demanding mentally, and not always particularly enjoyable because it means you are working on your weaknesses.
Musicians who practice in this way will benefit by becoming better, especially if repeated over long periods of time. Researchers estimate that a minimum of 10,000 hours is required to become a world-class expert in a given field.