I had the pleasure of "teaching" Joe at a workshop some years ago. He was already astonishingly fast and, more to the point, accurate and expressive. I used to leave these workshops having learnt more than most of my students!
I think hundreds of hours practice is about right but you also have to possess a natural talent to achieve Joe's standards.
When you get to my age you work on which notes you can leave out rather than "why play one note when five will do" - I call it maturity (or idleness).
Martin