Note: If you use the Import/Export Wizard to export archived items back to their original mailbox, the shortcuts in the user's mailbox will be replaced with mail items, so there will be no duplication except if the user has moved shortcuts around in their mailbox to other folders than where they were originally archived from.
If users have moved shortcuts around in their mailboxes the following will happen when you export back to mailbox -
1. items that were archived in a particular folder in outlook and not moved around will restore without an issue and restore the original items
2. items that were archived and then the shortcuts moved to a different folder will be restored as original items in the original folder where they were archived - not to the folder where the shortcut was moved to - this will result in shortcuts being left behind in the mailbox, those shortcuts will still work but they are essentially duplicates of the restored item and will need to be deleted manually. If the customer wants the structure they now have with the moved shortcuts - they can delete the restored item from the original place where it was archived and is now restored to and they can use the shortcut that is still in the location where they moved it, to restore the item to the location the shortcut resides in and then they can rearchive the item if they want. This will update the index with the item's new location.
Example
I have two folders in my outlook - Inbox and Test. I archive a bunch of items in Inbox and then move the shortcuts to test. If I do an export from archive back to mailbox I will end up with the restored mail items in the Inbox because that is where they were initially archived and it's the only location pointer Ev has to them in outlook (at the time of archive - after they become shortcuts we lose the ability to track them) - the shortcuts that I move to the Test folder remain there and are still accessible (I have not used the option to remove them from archive so they are still in the archive and can be accessed regardless of their location in my mailbox).