「～する限りでは」という意味の英語は as lon as と as far as があり、英会話において何かに関して自分の意見を述べる際にとても便利な言い回しです。ただ、使い方がややこしいです。 as long as は「時間の限度」と「条件」を表し、 as far as は「程度の限度」を表します。理解しにくいので例文で覚えるのがベストかと思います。
as long as : ① As long as he is here, I'll have more work to do.
② I don't care as long as you are happy.
③ I'll never forget this day as long as I live.
④ You can use my car as long as you drive carefully.
as far as : ① As far as I know, he hasn't been Australia.
② As far as I could see, the field was covered with snow.
③ As far as work is concerned, I always try to do my best.
④ As far as I can remember, I have never seen Ms. Ueda.