Zen master Joshu Sasaki Roshi, one of the original generation of masters to bring Japanese Zen to America, turned 100 years old in April - and apparently shows no signs of stopping. He still conducts (and personally teaches) 10 or 20 week-long retreats every year.
When the reporter from Tricycle asked him something, he said, "I am a hundred years old. My ears can no longer hear stupid questions."
The Tricycle article is here: http://www.tricycle.com/issues/editors_pick/4025-1.html