I only would like to keep the Access Logs of the last n days created by Tomcat Access Log Valve. http://tomcat.apache.org/tomcat-6.0-doc/config/valve.html#Access%20Log%20Val
By default rotatable is true for Access Log, so you will be having a new file created every 24 hours.
Tomcat itself does not do any housekeeping on the old files, the general principle on a Unix system is to have a cron job set up on the system to archive older files into a back up directory and/or delete them.