Recap about Deployment Re-evaluation Though name indicates what it does but still clearing questions if any.
Re-evaluation on Software Updates Client Agent reevaluates(Recheck) software updates for installation status helps when Computers offline/Added newly to collection or removed patches from computers.
Scenario: You have created A deployment with List of patches (100) and deployed to collection consists of 100 machines with deadline date 1 week from current date.
computers which are online and performs below actions based on the settings you choose before they get the updates like how many are required(missing) ,not required ,installed etc.
Software Updates Scan Cycle: Scans for software updates compliance for updates that are new since the last scan. This action does not evaluate deployment policies as the Software Updates Deployment Evaluation Cycle does. This is a forced online scan and requires that the WSUS server is available for this action to succeed
Software Updates Deployment Evaluation Cycle: Evaluates the state of new and existing deployments and their associated software updates. This includes scanning for software updates compliance, but may not always catch scan results for the latest updates. This is a forced online scan and requires that the WSUS server is available for this action to succeed.
Once the scan is done and policy arrives,Computer pass the time until the deadline(mandatory) is reached .When the deadline reaches,computers will start installing the required patches and reboot if necessary what you choose.
What happens to Computers which are offline/Newly Added/Updates Removed after the Deadline Expiration?
When computers (offline/New/Removed) come online and will perform Software Updates Deployment Evaluation Cycle,they see what is missed from the existing deployment and get them installed as mandatory.
For more information about Software Update Deployment Re-evaluation and how to Configure it,Read http://technet.microsoft.com/en-us/library/bb693813.aspx
Software Updates client agent settings http://technet.microsoft.com/en-us/library/bb632393.aspx