To answer your question, it would be much MUCH More common to be frail and weak at age 122. There are a lot more frail old villagers than super-ultra enlightened gurus or ancient super insane (I mean genious) Earth Bending kings. They're only two characters, it's really not that common. This post has to be over 300 characters so I need one more sentence. There we go.

Actually there is another person who outlived those two, and many of the avatars. Avatar Kyoshi was by far the oldest person on the show, living roughly around for 230. Yes she is amazing =D As far as alive characters I would have to say that the Guru is the oldest, and I must agree on the fact that it looks as if nothing will slow him down. In all honesty I would think a man in his 100's would become very frail, but seeing that a benders body is some what more fit then a non bender it may be possible for those benders to become weaker at an older age. In my opinion I think you should make him frail, I'm sure if I was 122 that I wouldn't be walking around at all xD

I have to agree with Auka, and thanks for staying 300 characters ;D I will also move this to the Characters Discussion Board seeing that it's more focused around characters then the actual show =D