If you do a lot of intensive retreats you will develop strong concentration. Many of the people I meet in America have been doing retreats for 15-20 years and they are really quite accomplished concentrators. But I'm afraid they have not found much freedom. We have learned how to concentrate our minds and then to push out our worldly irritations and responsibilities. We create this great space inside and become very good at getting rid of thoughts and feelings.
Meditation can thus become rather like being in a shooting gallery with the little ducks.
You can become a great marksman or markswoman, shooting down the thought ducks and the feeling ducks. One reason for the retreat emphasis, at least in vipassana circles, is due to the Asian systems that have fostered many of our teachers and styles of practice. Goenka-ji and Mahasi Sayadaw's disciples emphasize a very controlled retreat situation as the primary path. Retreat, retreat, retreat. Those teachers have had enormous influence and have helped tens of thousands of people, but I think that their style has led to this imbalance, the unhealthy separation between life and retreat.