I guess it's also one thing to know them, and one thing to be comfortable typing them in a nonstop flow of text. My keystroke speed rarely changes from insert mode to control mode; vim commands have become an integral part of my typing process. I feel severely gimped whenever I can't use my vim controls.

As for knowing the number of lines you need to jump, either do :set number and be quick at math, or you can modify the numbers to be relative to your current line.

I took me probably a week to be able to actually get anything done in vim, and a month to prefer vim to anything else.

That being said, I know far more commands than the ones I listed. Those commands got me to my first month, though.