Create a Thunderbird-like mail archiving feature in Mail

In my recent Thunderbird 3 usage, I've come to rely on search almost exclusively. I leave messages in my inbox until they are dealt with, and when they are dealt with, I just hit the 'A' key to archive them. Now I can do that with Mail.app, too.

When you hit 'A' in Thunderbird, it archives each message in a folder based on the date of the message, e.g. INBOX/Archives/2010 for messages from this year. The following AppleScript also does this in Mail. (The script will also mark archived messages as read -- Thunderbird's 'A' key does not do that.)

Copy and paste the following into AppleScript Editor:

on run tell application "Mail" set selectedMessages to selection repeat with selectedMessage in selectedMessages set msgDate to date sent of selectedMessage set msgYear to...