[Orgmode] Automatically "archive" todo-items that are DONE?

[Greg Wilson]

Hello, I am a new user, please bear with me.

I keep lots of TODO-lists in a file:
* project1
** DONE ...
** TODO ...
...
* project 2
** DONE
...

After a while, when the number of TODO-items that are turned into
DONE-items is high, the list gets messy and it's hard to find the
stuff left TODO.

What I would like, is org-mode to automatically move items that are
set to DONE into a second "archive"-part of the file, with mirrored
categories from the TODO-lists. Let me show you an example:
* project1
** TODO ...
** TODO ...  <-- no more TODO items here, because...
...
* project 2
** TODO
...

* project1     :ARCHIVE:   <--- ... org-mode moves DONE stuff down
here and adds tag.
** DONE ...  :ARCHIVE:
** DONE ..   :ARCHIVE:
* project2     :ARCHIVE:
** DONE...   :ARCHIVE:

This way, the TODO-lists always lists stuff that you actually have to
do, not cluttered with stuff that's been done.

Is this possible? Would it be hard?

Thank you for a very nice piece of software! /Greg