Initiate new phase 2 all 48 minutes

[Chris-H]

Hello.
in my logs i see some strange things.
I dont know why this happen.
It is a site2site VPN between pfSense 1.2.3 and a SonicWall.
The setup is like the example in the definitive guide.
Both WAN IP are static.

May 12 10:12:03 thor racoon: INFO: IPsec-SA expired: ESP   (IP addresses cut off)
May 12 10:12:03 thor racoon: INFO: initiate new phase 2 negotiation:
May 12 10:12:03 thor racoon: INFO: IPsec-SA expired: ESP/Tunnel
May 12 10:12:03 thor racoon: INFO: IPsec-SA established: ESP
May 12 10:12:03 thor racoon: INFO: IPsec-SA established: ESP
May 12 11:00:04 thor racoon: INFO: IPsec-SA expired: ESP
May 12 11:00:04 thor racoon: INFO: initiate new phase 2 negotiation:
May 12 11:00:04 thor racoon: INFO: IPsec-SA expired: ESP/Tunnel
May 12 11:00:04 thor racoon: INFO: IPsec-SA established: ESP
May 12 11:00:04 thor racoon: INFO: IPsec-SA established: ESP

This happen all 48 minutes
The Phase 2 livetime is 3600 seconds on both sites
ok the tunnel runs fine  ;D  but i want to know whats happen here.
Anyone see this before ?

Chris