Every object has an extra attribute called expirationDate.

This is the date after which the object will be considered "expired".

You can show this extra attribute in a Directory Style this way (this example shows folderObjects):

...

<ColStyle Name="Expiration" Width="75" Height="0">

  <CellTemplate>

    <xp:TextBlock VerticalAlignment="Top" Height="Auto" Text="{Binding Path=[folderObject:expirationDate]}" />

  </CellTemplate>

</ColStyle>

...