This is a question I get quite often from my clients. And my answer is…it depends.
I once heard a rule of thumb was once every 2 years. I am less likely to look at the passage of time and more at whether your website is effective or not.
The first question you should ask yourself is, are you getting the results you are expecting from your website? If the answer is yes, then you might look at some ways to incrementally improve your website by changing content that is outdated or adding information about some new promotions, products or services you have added. If search engine optimization is your main concern, then maybe a change in technology behind the scenes is the key to a successful redesign.

SEO + Analytics