I had the same issue as you did @xlr8r. I can tell you right now that it comes down to two issues:
1) The router is having issues with DHCP when it comes to assigning local IPs to devices in your network, thus causing it to disconnect everything.
2) The router is having issues with DHCP when it comes to leasing a new IP when your ISP decides to change the IP address to your network from the modem. A lot of ISPs work on dynamic IP addresses, which means that every so often, your IP lease will end and your IP address will either be renewed, or get changed entirely from their end to your modem.
Once I said, "Screw it!" and got an EdgeRouter from Ubiquiti, I used the Nighthawk as a simple access point, and the internet has been working perfectly fine. This leads me to believe that one of the two things I listed above are the issue with the Netgear Nighthawk router disconnecting all the time. I believe its most likely my second point, simply because when it does disconnect, I reboot the router and then it has problems getting an IP from the modem period. It tells me that the cable is disconnected and to check the modem to see if its working... I have to reboot the router a few times, plug the WAN cable out and back in for the router to get an IP from the modem again.