Your website is never a finished article, there are always constant tweaks and improvements you can make. Take a look at our article “http://www.voovadigital.com/4-common-seo-mistakes-marketers-make/” for more infomation. And from an SEO point of view there is no stopping constantly split-testing every element.
But in reality, unless a professional digital marketing company is engaged to do this work, only so much time can be devoted to this.
Here is a quick guide how to do auditing on a regular basis.