Exchange Intelligent Message Filter

I have just started using the Intelligent Message Filter on Exchange 2003 and have set my gateway threshold to archive the spam to the front end server. I am concerned about automatically deleting necessary email. This way I can go through the email if someone is missing something. Does anyone know if it is possible to automatically clean up the folder where it stores the spam email? I would like to set it to automatically delete the spam if it is older that 1 week. Is this possible. Thanks.