as long as, as far as

いずれも和訳ならば「〜の限り」といった感じだが、２つは意味合いが違う。

as long as　条件を示す

as far as　範囲を示す

I will tell you the truth as long as I can recall.

I will tell you the truth as far as I know.

こんな感じ？