DHCP request every 30 seconds ? - log file

I have just connected a D-Link DI-614+ router to my modem. Everything works
fine but when I look at the log file for the router I can see that it is
sending a DHCP request every 30 seconds and then getting "success". Is this
normal or have I stuffed something up?
I read something about RIP updating every 30 seconds but there is no mention
of DHCP requests before the end of a lease.
Rang D-Link today and im waiting for a return phone call from their tech
support.

cheers - Graeme