I was playing pop music a lot, then decided that I wanted to master classical music.
I practiced dilligently for about 2 hours a day, then passed my gr. 10 2 years later. I should have my Arct in another year. (things take so long with all of the co-reqs) So to answer your question, 2 years sounds about right if you take it seriously and spend a lot of time practicing sight to make up for lost time.
As for mastering, the piano, I think I've given up on that....

the closer and closer I get, the more I realize that ARCT is really just the beginning.
