We keep a copy of the recovered data for 30 days after it has been shipped. It is possible that your return shipment will be misplaced in the mail or that the return media will arrive damaged (both of which are extremely unlikely scenarios), and we will be able to prepare a second shipment if something happens.
We do not, however, keep data for an indefinite period of time. Following the guidelines set forth by the National Institute of Standards and Technology (NIST) for data sanitization, we securely destroy all client backups.