After launch, don't forget to evaluate your website for usability. How does your site navigate? Are there any issues? Google analytics is the premier software for analyzing users, landing and exiting pages and click through traffic on your site. Why not take advantage of it and learn as much as you can?
Jakob Nielson, from Nielson Norman Group recommends a company spend on average 10% on usability and states that
"On average, this will more than double a website's desired quality metrics and slightly less than double an intranet's quality metrics."
We can have great graphics and wonderful products services but Nielson states simply that if a site is not usable, people leave.