The default aging periods for folders are:
Inbox, Calendar, Tasks, Notes, Journal, Drafts: 6 months
Sent Items, Deleted Items: 2 months
Outbox: 3 months
Note Folders you create that contain the same type of items as Inbox, Calendar, Tasks, Notes, or Journal are subject to the 6 month aging period, too.
The way Microsoft Outlook determines the age of an item varies based on the item type.
E-mail message
The sent or received date or the last modification date/time, whichever is later.
Calendar item
The appointment, event, or meeting date or the last modification date/time, whichever is later. Recurring items are not AutoArchived.
Task
The completion date or the last modification date/time. Tasks that are not marked complete are not AutoArchived. Tasks assigned to others are archived only if marked complete.
Note
The last modification date/time.
Journal entry
The date the journal entry was created or the last modification date/time.
Contacts
Not archived.