So I have one and have been using it for a while now. It gets really dirty quick (It has attracted tons of dust and dog hair). And I hate to keep washing it, so I took it off. Should I continue to use it after washing it or just leave it? The keyboard cover leaves alot of marks onto the screen, which makes me constantly keep cleaning the Aluminum MacBook's screen. Is the keyboard cover really necessary? I don't want dust and dog hair going into my keyboard keys.