The only way is to
        1) retrieve the files and re-archive with a management class of the
desired retention
        2) DO NOT RUN ANY "EXPIRE INVENTORY" and then I won't guarantee
anything...
        3) Rename the node, set up another domain with an archive grace
period of how long you need the data, that DOES NOT have the management
class to which the files are currently bound, and move that node over to
that domain...
        AND I WON'T GUARANTEE ANYTHING... and you will still need to
re-register the node as it was before.

Yes, we need to be client focused but a lack of planning on their part does
not constitute an emergency on ours...

Also it is a security thing... if you could extend the retention period, you
could also reduce it.
Granted we, as admins, can just delete it, but having things as they are
does provide a little extra security.

Dwight