Hi,
neither Alfresco itself nor the standard clients (explorer, share) does provide an offline functionality. You might try out the microsoft function "Make available offline" for network drives (using CIFS or Webdav) or the Microsoft robocopy tool, I never testet that with alfresco drives.
Or you check out the alternate clients, beeing developed in the community : Flexspaces, Opsoro, Docasu, I think they plan for that.
Let us know what your testresults are.
Norgan