I have been studying Rocket German for about a year and a half. I did, however, get away from my studies for 3-4 months, for personal reasons. When I returned to my studies I began by reviewing previous lessons. I was very surprised how much I remembered. This I would have to say supports how effective the material is in the way it is presented...I was not expecting to have retained so much of what I had studied, after being away from the course for so long. The course is definitely worth the money and I have recommended it to several other people