By creating a new management class with the appropriate retention settings
for the domain that node is assigned to, then on that node add an include
statement appropriately pointing to that managementclass..

e.g.

include /somefilesystem/.../* newmanagementclassname
include /somefilesystem/* newmanagementclassname

everything for that filesystem will use the retention settings of the new
mgmtclass.
Everything else will use the default management class.

Gerald Wichmann
Senior Systems Development Engineer
Zantaz, Inc.
925.598.3099 (w)