I use a disaster recovery plan for each client based on their ability to "know" where the archives are and their permitted recovery time. The issue of knowing where a backup is and its validity is a business process issue. It is one of those holy grail issues that are covered by corporate compliance and verified by the audit team. I recommend an internal replicated SharePoint site for those memory joggers with hardcopy (yes, paper) of critical pointers stored off-site in the organization's bank safe deposit box.

Usually, the required "back on the air time" dictates how "near real time" the archive backups are. In general the archives are read verified, if stored on-site, at a low priority as part of other regulatory compliance processes (SOX, ISO 9000, etc.). If the archive backup is off-site, then a new archive backup is created to the same schedule as the organization's fiscal reporting, usually monthly, or at a minimum annually.

FWIW, the disaster recovery plan (or business continuity if you prefer) is usually required for the organization's Errors and Omission insurance and sometimes its liability insurance.

Regards, Ira