Why do we continue to practice aikido after green belt?

This was originally posted by John Kirby on the Karl Geis forum.

Karl briefly mentioned at the past summer clinic that a fugakukai green belt can perform adequate self defense. So why do the rest of us continue to practice and work on refining what we already know when we have gone beyond greenbelt training?

Are we going for something other than self defense? For 'better' self defense? If you quite practicing, do you lose the self defense capability? Do we get a joy out of those (for me, rare) aiki moments when uke is effortlessly thrown and you both wonder what just happened? Other reasons?

This past week that I have been asking and pondering this question locally and have recieved what I believe are fascinating and sometimes very personal answers. I do not believe there is a 'right' answer to this question but I believe the answers provide very interesting insight of the people practicing in our orginization.