It is really important to have a strong relationship between the website owner and the web designer. The two of you need to work together to enable the website to work properly. It is not just a case of building a website and leaving it alone.
If it is based around Joomla or WordPress these programmes and plugins get updated all the time and they need upgrading to keep the website working properly. But also keep in mind can the template take the upgrade has its development kept pace.
One of our clients has a website that has continuous menu changes each month and for their theme nights. To make it work the design of the website menu structure enables easy up dating of existing themes and months, we just change the menu items and turn on and off in the navigation. Once all the menus have been created we can easily manage any up dates.