I just saw this article…Makes me wonder if we’ll get a free archival tool from MS for OpsMgr ACS someday soon?
When using System Center Operations Manager 2007, the audit database data retention period is set to 100 days but Audit Collection Services (ACS) reports return no more than 42 days data.
The ACS collector service uses DbCreatePartition.sql to create the partition tables and DbDeletePartition.sql (C:\Windows\System32\Security\AdtServer on the Collector server) to delete the partition tables based on the retention period. It also creates the views AdtServer.dvall, AdtServer.dvall5 and AdtServer.dvheader. In DbCreatePartition.sql and DbDeletePartition.sql, the dvall , dvall5 and dvheader views use a union of only the top 42 partition tables.
Read more at http://support.microsoft.com/kb/2663919
More on ACS on the WIKI
Read more about ACS on the site wiki at http://www.systemcentercentral.com/WIKI/WIKIDetails/tabid/146/IndexId/20526/Default.aspx