Currently it is not possible to archive audit logs.
Archiving in the sense of remove logs in a structured organized way with the possibility to restore this information at a later time if needed.
This feature already exists for session logs (although could be improved) but there is nothing similar for audit logs.
We already have an audit log of 13 GB, by far the largest table in our DB.
There is a script available that should reduce the size of audit table by removing change history details (ie object XML), which is permanent loss of audit information.