Ed,

Wayne is correct.
You can hower adjust the current applied retention category but this will not solve your case I guess.

Regards,
JB

From the EV 8 ReadMeFirst:

With Enterprise Vault 8.0, when a user moves a shortcut to another folder in an Exchange mailbox or changes an item's retention category, the change is reflected inside the archive.

Does this mean that you can change the Retention Category retention parameter that the archived item was originally archived with and that item will have the new retention parameter? Or is it possible now to assign a new retention category and its parameter to an already archived item

If by retention parameter you mean the number of days/years then no that is not what this means.  That is changed on properties of the Retention Category.

It will change the Retention Category assigned to archived item.  So for example, your archived items all have a retention category of Business and it is set for 3 years.

You can create a new Retention Category called 7 years and set it for 7 years.  Then create a folder via EVPM in the users mailbox and assign that 7 year retention category  to it.  Users then drag archived items into it and when the mailbox process runs it will assign the 7 years Retention Category in place of the Business category that was assigned to it.

Hope that is clear..:)

That is correct and updatable meta data will also reflect the new folder location however you cannot guarantee to catch everything as users delete shortcuts so there is no guarantee,

You can use EVPM to associate different Retention Categories to different folders and the updatable mettadata will then inherit the new Retention, but take "Deleted Items" for example there will be millions of shortcuts deleted from the Deleted Items so will therefore not get updated, and will still have the "default" Retention Category set.

--wayne

Running some tests on this now to ensure it will execute as I am hoping it to