didn't take me too long, i guess about 1-2 months.
I have played about 400-500 games so far. ( I hate the leaderboards reset!! )
I wish you could do over the ranks, because whenever i join a match and my teammates are generals too the opponents quit the match. Very stressing to find another match because it takes ages sometimes.
But, at the same point, those Generals could be the "weak generals". I consider those the Generals that don't seem to know what a General should know.
Honestly, it took me a year. The score drop definitely helped me get there.