Allow documents to expire

It would be nice if one could set an expiry date for documents to disallow unintended changes after a period of time. The expiry date could have different modes, e.g. to lock the document, or to delete it completely. Additionally, I'd like to have the option to set this globally for all documents. So, for example, I would like to be able to declare that all documents can be edited for only one week after creation.