Thank you for the information!

http://802.11junk.com/jeffl/crud/DHCP_querytool_free.exe
That's the free Weird Solutions DHCP query tool which is no longer
available on their web pile. Install it and run. Put any manner of
garbage in the "Device Identifier" box. The output should look like
this:
http://802.11junk.com/jeffl/crud/DHCPQueryTool-output.jpg
option DHCP address lease time=86400
option DHCP renewal time=43200
option DHCP rebinding time=75600

The renewal time is always 1/2 the lease time.
Lease time = 86400 seconds / 3600 sec/hr = 24 hrs
Renewal time = 43200 sec / 3600 sec/hr = 12 hrs

The rebinding time (time to retry if renewal fails)
75600 seconds / 3600 sec/hr = 21 hrs

How it all works:
http://www.tcpipguide.com/free/t_DHCPConfigurationandOperation.htm


I strongly recommend Karp's "Windows 7 Annoyances". It's actually an
intermediate-to-advanced user's book on configuring Windows 7. It's one of
those one-in-a-hundred techncial books that's easy to read and understand,
without being superficial. I can't recommend it highly enough. Everyone who
wants to be sure their computer is doing what /they/ want it to do needs a
copy.

I feel sorry for Mac owners. They seem to be afraid to lift the lid and get
their hands dirty. Well, I want to know /what/ the OS is doing, and /why/.