For me, the most important thing is the element of chance that is built into a live performance. The very great drawback of recorded sound is the fact that it is always the same. No matter how wonderful a recording is, I know that I couldn't live with it--even of my own music--with the same nuances forever.
If you've never felt that you quite got a hold of it, you just feel that before you die, you've got to try and get it right once. And hope that the experience you have makes up for the some of the diminishing energy.