In order to Auto-Archive in Outlook 2011, you will need to set up a rule within the program. Please see the steps below on how to do this.
1.) Click on Rules on the top toolbar.
2.) Click Edit Rules in the list that comes up.
3.) Choose Exchange listed under "On My Computer"
4.) Click on the + sign at the bottom of the screen.
5.) Give the rule an appropriate name such as "Auto Archive 180 days old emails".
6.) Change "When new mesage arrives:" section to "Date Received" "is" and then the amount of days back you want to archive.
7.) In the "Do the Following" Section set it as "Move Message" and then choose the local folder you want to move the emails to.
8.) Click on the minus sign next to "Set Category" "None".
9.) Make sure the check box in front of "Do not apply other rules to messages that meet these conditions" and "Enabled" are checked.
10.) Click "OK"
The rule(s) will need to be manually run when ever you want the Archive to run.
If you want to keep the emails in seperate folders on your system you will need to create rules for each folder.