During the installation of each of the EBS 2008 servers, you will have two update phases, one is required and the other one depends on whether you select the option “Download and install optional Microsoft updates during installation” or not. But you may not receive the most recent updates from Microsoft Update in two update phases. By default, after EBS 2008 is installed completely, EBS servers will get updates from Windows Server Update Services (WSUS) managed by your system administrator. It depends on the updates available on the local WSUS server.
More info: Microsoft Updates