Drills are the stepping stones of efficient and competitive swimming. They are specific movements, which are done repetitively, to improve your technique. Better drills lead to more efficiency meaning less energy output. Along with endurance they are the keys to you becoming a better, faster swimmer. Drills are a part of every workout. There is no end point of when you have nothing more to improve or that you have exceeded the need for technique work. You ALWAYS have to work on drills, and once you master them, you have to CONTROL and MAINTAIN that FEEL!