If you do not wish to keep storing all of the logs, or 'system actions' that are happening, there is a custom Django command you can run to remove them after a certain number of days.
python manage.py system_action_cleanup
That command looks for the DAYS_TO_LOG_DELETE setting in settings.py and removes any logs after that amount of days. If you wish to run a cronjob, edit your crontab file with this
DJANGO_CONF=conf.dev
0 0 * * 7 /path/to/project/env/bin/python /path/to/project/manage.py system_action_cleanup > /dev/null 2>&1
This job runs cleanup every Sunday at midnight. You can edit it for any time you wish (checkout the cron help pages online) and also write any output/errors to any file you wish by replacing '/dev/null' with the file path. Also, make sure the two lines above are own their own separate lines, and they don't exceed one line individually. The job must end with a line feed (press ENTER)