My Sensei, and his Sensei, I believe, think that if you at least learn the movements of the kata you can than work on learning the secrets. You will learn all of the katas as long as you keep attending, ofcourse you might be a 5th degree BB before a couple are shown to you.
The more advanced the kata is the harder some of the movments are so they can be taught sometimes to more capable students than old fogies. No offense to anyone. Also, to like ya said, keep em alive, and fresh, and as part of Goju that is in you.
Our kata system goes from the fukyu katas, which are the basic, to the Gikisai dai ichi, dai ni, seifa, seyunchin, shisochin, sanseiryu, sepai, kururunfa, sesan, pychuran, and than sanchin and tensho katas. (my spelling is probably messed up on some of em, and the order as well. I might have forgotten one I am not sure)
May the force be with you.