So the issue with our computers DCing every 12 hours was caused by me setting static IPs for them in the router.
Router not meant to handle it? Or was it releasing them constantly?
One of my previous jobs used a piece of equipment we referred to as infoblox, I believe it was an "appliance?" My only real complaint with it is that it was really slow and sometimes the page lagged out, but that may have been due to the sheer size of the network.
I totally do the same with my router at home though, have tomato by shibby on a linksys e3000, it works rather well (did it on an old wrt54gs before this one too).