A friend of mine is a sports physiotherapist. He's pretty good at this and has worked with premiership footballers, Belgian international Squash players and others. Apparently it's common knowledge in his world that all top sportspeople put in around 10,000 hours practice before they reach the top. That's about 20 hours a week for 10 years. He emphasises that this was practising as distinct from playing the sport. One key difference is the continuous involvement of a coach to make you do it right.
What does this mean for programmers? I think that pair programmers have a coach present, and so they're building their 10,000 hours. On this basis, 10,000 hours of pair programming makes you an international. No amount of lone programming gets you there though - you're just programming.