Classified Ads exposes the ad expiration "extra-field" as a CTools content type.

In practice, this means you can add it to a custom-built page in Panels just like core Fields.

The field has two settings:

- `link` defines whether or not the expiration "field" should link back to the node URL.
- `format` defines the format under which the expiration "field" should appear: either as a remaining lifetime, a remaining percentage, an actual expiration date, or using the default formatter used for the normal node view.