Here's a little script you can add to your crontab, to periodically email the administrators of each mailman mailing list both the list of current members and the mailing-list's full configuration. This gives you both an audit trail of membership and the ability to restore mailing lists from the backup files in case your webhost goes awry.
mailman-reminder (Perl script)
Edit root's crontab with the command
# **crontab -e
and add something like this:
0 3 1 * * perl /root/mailman-reminder.pl
Which will run the script at 03:00 on the first day of each month.