After an Alpha site is released, there are typically revisions. This is due to the fact that until an actual website is released it’s hard to know fully how it will look and work. The different types of revisions include preferences for how a page responds on a particular mobile device to how a page looks when it is fully populated with content. The more time spent in the Definition phase specifying functionality and using advanced ‘live’ wireframing will reduce the amount of time needed for revisions.
Review how much time is included in the Project Plan for definition and revisions. 15 - 30 hours is often needed if the site is reviewed by multiple people, includes a RWD and functional features.