Once your new vanity's installed, you will need to look after it to preserve its appeal. Cleaning your vanity regularly is important not just for the sake of hygiene, but also to prevent long term staining. A well-polished mirror can add a spectacular highlight to your bathroom as well, opening up the visual space and enhancing the existing light.
A clean bathroom mirror will affect how big the room feels, as well as how much light is reflected throughout the bathroom.
Cleaning your vanity is good for hygiene - it's also a way to prevent permanent stains, and to keep your bathroom looking good.