I've had the C6300 for over 5 years and never could figure out why the 5ghz always disappears after couple hours of rebooting. Finally think i fixed it. I also just upgraded my plan with Xfinity from 200 to 400 MGB so don't know if that has anthing to do with it but has not disappear for 2 days. Here is what i did.
1. log into Netgear genie and go into the menus
2. Click on WiFi Connection tab on left hand navigation side.
3. Click on Manage. you wll see the list of WiFi connections available.
4. Click on the 5ghz WiFi and click Move to the very top spot
5. Click on the 2.4ghz and move that to number 2 spot
The number#1 spot is always set as the default. So far the 5ghz has not disappeared.
