Impact of not port-forwarding 5060?

My VoIPo service works fine, but with my new router, I see errors in the router's log on inbound (to me) traffic on ports that I don't have setup as port-forward. Apparently it doesn't matter. What does it affect? In the below there are three different Internet hosts sending traffic to me on port 5060 which is VoIP related, but since these were dropped in the router, it apparently matters not??? (I use an ATA, not Asterisk)

[INFO] Wed Nov 10 19:14:06 2010 Blocked incoming UDP packet from 174.37.45.134:5060 to xx.xx.xx.139:5060
[INFO] Wed Nov 10 19:14:02 2010 Blocked incoming UDP packet from 208.43.68.151:5060 to to xx.xx.xx.139:5060
[INFO] Wed Nov 10 19:13:53 2010 Blocked incoming UDP packet from 174.37.45.134:5060 to to xx.xx.xx.139:5060
[INFO] Wed Nov 10 19:13:49 2010 Blocked incoming UDP packet from 208.43.68.151:5060 to to xx.xx.xx.139:5060
[INFO] Wed Nov 10 19:13:27 2010 Blocked incoming UDP packet from 67.228.77.18:5060 to to xx.xx.xx.139:5060

Those are keep alive packets from various VOIPo servers. The NAT connection will not stay open on a lot of routers unless we send near "pings" to it to keep the connection open.

As long as your device is staying registered, those aren't needed.