No, his convention appearances date back 40 years. In a biography I have been cobbling together from interviews, introductions, and similar sources, I wrote:

"In the early decades of his career, Vance avoided talking about himself or his writing in the belief that knowledge of the writer might predispose a readers response to the work. But he was no recluse and enjoyed meeting people, even his readers. When David Alexander learned that Vance was a fellow Bay Area resident, 'with some trepidation I called Jack and asked if I could meet him. He said that I could, provided that I did not talk to him about writing.'

"Vance does not truly merit his reputation as 'the invisible man' of science fiction. He has been a guest of honor at more than ten conventions, from Westercon in 1962 to Norwescon in 2001, in locations spanning the globe from Sweden to Australia. In the later decades of his career he also has given an increasing number of interviews, going so far as to write an eight-page autobiographical sketch in 2000."

This bio is far from finished, I peck away at it from time to time as some bit of information comes to my attention. Perhaps when it is ready, one of the Vance web site hosts will kindly post it.