It depends on the definition of "know". My sensei says that in order for us to "know" a kata... we must be able to: Perform that kata from start to finish, without mistake, 98% of the time. Perform the attacker and uke portion of the prescribed bunkai for the kata. (bunkai is the practical application of every move in the kata) Be able to improvise one's own bunkai that is different than the prescribed bunkai. Under this definition, after 6 years of training, I only know 6 kata. Knowing the moves, and knowing the kata, are two very different things. I remember when I first started learning Taekyoku Shodan thinking- there are only 28 kata??? That will be easy... I am SKIF and we have to know: 28 Kata Kihon Kata Sanbon Kumite Kihon Ippon Kumite Keashi Ippon Kumite Jiyu Ippon Kumite It is a full time job to stay current on the stuff I "know". If you don't use it, you lose it, and there is a LOT of curriculum.