Why do I get these messages almost constantly<>(over 100 yesterday alone)? The RF600VPN is up and running fine from what we can tell. If I reboot, they'll stop for maybe a half a day; then start up again.

This happens whenever the PPPoE connection goes down and the RF600VPN has to reconnect. It is possible that your PPPoE connection gets disconnected due to idle timeout and the RF600VPN has to reconnect to keep the link alive. When your link is down, it will try to reconnect every 5 minutes. So, as it tries to reconnect every 5 minutes, it will send out a notification each time. "Keep Alive" is always set and that is why the RF600VPN will always try to reconnect when it senses the link is down.