In as little time as a month, it is possible to start seeing measurable results not only in the number of potential customers that are driven to your website, but also (and more importantly) in the number of sales that your e-commerce site generates (conversions). A change in the content and a cleanup of SEO relevant tags in an established site can boost both traffic and sales by as much as 40%.
Does this apply to all scenarios? No, of course not. But with careful SEO analysis, you will be able to determine how much you can stand to gain from an SEO housecleaning..