Funny, this subject came up on another list and the figure given to reach the elusive 'mastery' was 2,ooo hours. A term that I labeled ridiculous. Since the levels on ALL things in our world keep going up, it only serves to prove that mastery is NEVER reached. I took a lot of heat for it.
When one reaches the level 'Master Mechanic' the pay scale at that level doesn't allow mistakes. If you make mistakes, you are a 'Journeyman'.
It's like Segovia said when he was in his late 80's (paraphrase?) "I think I'm close to getting it".