I had a Japanese conversation course for only 1 year at the Japanese embassy in Berlin. I forgot everything except "tenki wa ii desu ne". Still it was a very good experience, because the politeness system built into the language is very interesting and there were many other interesting phenomena (like particles for count systems, topic marker, etc.) that helped me later for my work in the philosophy of language and semantics. I also learned a lot about Japanese culture in that short year.