Managers, oh joy...
Anyway. I agree with Virgil. You need to test to see if you do not get duplicate items in the archive. And, if it works at all. The thing is, if you archive an item, I believe it does get a stamp somewhere, something like 'is archived'. This means that if you try to archive the item again a year later, it won't archive because EV already has it.
Again, I'm not sure, but it is worth a test. Taking in account the timeframe, you should be able to simulate it in 2 days right? Depending on the requirement, would it be feasible for this 1 person to:
Archive all items older than 1 day. Create shortcut, where content is messagebody, replace attachments with links. That way, the user has close to everything in the archive, and you have some control over the mailbox-size.