It takes years to become good enough to be classified a hacker. Even then, you might not be classified as one.
If you are talking about the actual knowledge, it can take 5-10 years to become "l33t", but in 2-3 you'll be decent.
But yeah, I'm nowhere near finished.
Basically, if you want to be a 'hacker' then you have to be committed. But then hacking is about the love of knowledge, so that should come naturally.