Just like your wardrobe, websites can need "a fresh look" for a number of reasons. They can be out dated, broken, tired, or just plain not fit your organization anymore.
Are you considering a redesign just for the sake of it? If so, you may want to reconsider. Being bored of your site isn't a good enough reason to redesign what may be a perfectly good website. If your current site has traffic and a good conversion rate, you should probably not redesign it.
Redesigning your website is like performing plastic surgery on it. Your website loses its current identity (for the better or worse) and your regular visitors might not recognize your new design at first glance. You risk losing them just because they thought they landed on the wrong page. Hence, it is very important that your brand identity be maintained throughout the redesign. Logo, colors, and brand message are critical.
The best way to know if you should redesign is to ask! Ask your customers, and if they think it is necessary for the website to have a fresh look, give it to them!
