You should be able to create a daily or weekly cron job to clean up these log files, however, it might be a good idea to figure out why the log files are getting so large to begin with ...
If your server is filling up multiple gigs of log files in a weeks worth of time it might be caused by a misconfiguration and the logs are merely a symptom of the root cause.
If your server is being attacked (even if attacks are unsuccessful) it could cause you to get a large number of logs. Installing fail2ban might be worth while.
If you really do not care about the logs and just need them to not fill up your harddrive, you could create a symlink to /dev/nul ... although this is NOT recommended.