Some installers – such as those for alpha, beta, or test versions of a product – need to expire to prevent use after a given date. While the installed program can (and should) time out, it would be frustrating and bad form to let a user install an expired program.
This can be implemented as an optional variable:
<!-- Make the installer expire -->
<variable name="InstallerExpiresDate" value="2016-01-01" />