If you have your heart set on it, be sure to register your interest in kaiseki after boarding. It often sells out, if there are any japanese pax on your particular flight. As for changes, seasonality is key and there are 4 different menus ... with the winter one being considerably more austere than summer, for example. Still think spring menu is the best, also that it isn't as good as it used to be (maybe 70% as good -- which means it is still quite good, but no longer quite as special as it was 5 years ago).