I've heard Willie in person four times (so far!) in four widely varying venues, from the Coliseum in Seattle, Washington, to the Coliseum in Wichita, Kansas, to a football field in Guthrie, Oklahoma, in October (and damned cold it was, too). He's never failed to put on one heck of a good show. Hard to recall the man's nearly 70, even with that "rode hard and put away wet" face of his.
Steve, I think you're right; he just loves to perform. And BTW, his new book is pretty darn interesting--and funny, too. Great pictures from a long career. Go make your local bookstore stock it.