I never reboot my NVRs. I have at this time currently installed and working 85 separate NVRs all based on Windows of some flavor and I have no reboot need on any of them.
Some I'm sure are rebooted by power outages and the like but we do have UPSes installed at all locations, but no specific reboots are needed for any of them. Some have been up for a long, long time and some I have literally never been inside since they were installed. I do everything remotely so pulling footage and the like is remote, no need to be in the machine. My machines almost all run local quad rotations all the time so the client is in use too so pretty normal usage. Still have many locations that basically run themselves autonomously and I cannot remember really having to ever specifically mess with. Only time I mess with them in general is when adding or changing cameras maybe.
I have the ability to remotely power cycle the NVR machine as needed via UPS, or via web power switches and at times I reboot other equipment on site via UPS so the whole site gets rebooted no matter what, but I can only think of one or two times where I rebooted a site due to a PC based NVR acting up.