I recently purchased the Netgear CM1150v and after it's been on continously for 12-24 hours my speeds drop to around 25 Mbps. I then restart it and my wifi speeds instantly go back to around 300 Mbps (I'm on the gigabit plan). I thought it might be my router so I replaced it and the exact same thing continues to happen. This wasn't a problem with the Xfinity supplied modem so I'm not sure why this is happening now.
For a test, does a computer hardwired directly to the 1150V modem (no router or WiFi in the mix) have the same problem ?