OK so while writing my book, I somewhat wished i had an easy way of defining the expiration "policies" via configuration while creating my samples for the Caching Application Block for Enterprise Library. This drove me to creating the the Caching Expiration Policy Application Block.  Its an application block that will support the Caching Application Block.  its sole purpose is for you to define Cache Expiration Item via configuration. It allows you to define multiple expiration items for a policy and define the attributes of each expiration item via configuration.  It supports all of the caching expiration items that come with the Caching Application Block.  I will soon (probably this week) be adding it to the Enterprise Contrib project on the CodePlex website www.codeplex.com. It contains runtime configuration only so you have to define everything manually in a  configuration file, but I intend on adding design-time configuration components as well so that it may be configured via the Enterprise Library Configuration Console/Editor.