Windows 10 Pro box hangs every 10-14 days or so...

Interesting... so the main stream is only used during motion? And if I have motion on all ten cameras at once?

Nope, from the wiki:

The main stream is used for:
  • direct-to-disc recording
  • single-camera live viewing and recording playback
  • audio
The sub stream is used for everything else:
  • multiple-camera viewing
  • motion detection
  • alert snapshots
  • etc.

None of us have missed motion as a result of using the substream option. But its savings on CPU is tremendous.
 
I am not using a VM with BI... Running Windows 10 Pro bare metal. I'd love to virtualize the whole thing but the Intel Sync passthrough was a hassle. I virtualize Windows 8 on ESXi to run HS and it is fantastic. Stable and maintainable.

I am sure Win 10 is super stable in most configurations but that hasn't been the case for me. This hardware was my old server so it has ECC memory, redundant drives, redundant power supplies, a XEON process and the like. It should be far more reliable that the refurbished Office machines most people are running on. That said, power supplies and hard disks don't have an infinite MTBF, so if the latest set of configurations didn't fix it-- maybe I'll upgrade those parts and do a fresh install.
Your system sounds old.... The used desktops we are using are SUPER reliable. I use them for BI and office systems. With the office systems I have hundreds in use, zero failures. Just because something was designed for a server doesnt mean it wont have issues. You are better off power savings wise to spend 100 bux on a i5-6500 elitedesk.
 
I have to chip in and say that I also have no issues with my windows 10 pro that I run homeseer on one box and BI on another. Homeseer had been running for over 4 years. My BI install is newer, but my computers all run newer hardware that was built for each other at time of construction. I am not the biggest fan of windows, but like others have mentioned, it could be all the ‘spare parts’ you are running.
 
I have to chip in and say that I also have no issues with my windows 10 pro that I run homeseer on one box and BI on another. Homeseer had been running for over 4 years. My BI install is newer, but my computers all run newer hardware that was built for each other at time of construction. I am not the biggest fan of windows, but like others have mentioned, it could be all the ‘spare parts’ you are running.

i have not ruled anything out. The fact it runs for weeks and then crashes is the worst to debug.
But the fact that I might be able to go back to a virtualized environment due to sub streams is hugely attractive. I’d rather invest in one powerful server for all my instances.
 
I have a dedicated BI machine. I have another machine that runs my home automation system (CQC), a DVR system (SageTV), and my IP phone system that runs on a virtual machine running Linux on this Windows machine. Both of those computers are "mission critical" in my house and both run flawlessly. I even have automatic updates turned ON because I haven't had issues and I want my machines to be as up to date as possible without my intervention. These machines run so reliably that I rarely RDP into the machines, so updating them manually would be a pain in the ass.

Now for the sake of complete transparency, my son had an issue with his custom built gaming system recently that caused the sound to stop working (the machine recognized his hardware, but failed to be able to use it). Personally I think it was a registry issue that might have been caused during an update. He did have to reinstall Windows 10 to get everything running again. He even bought a sound card during this process and the new hardware wouldn't work until he reinstalled Windows. However there is no telling what might have happened with that computer - He built it, he uses it, and I never look at it. The other 4 Windows 10 machines (not including the BI or automation computer) that are all used daily (two laptops and two desktops) haven't had any issues either. So out of the 7 Windows 10 machines we run in our house, only one has had an issue that I can remember - the sound driver issue that my son's gaming computer experienced recently. All 7 computers have automatic updates turned on.

Long story short, the days of blaming "Windows" for issues is long gone. Windows 10 is extremely reliable. That being said, it is a computer system and it is possible that something got corrupted - either in software or hardware. I'd start out by reinstalling Windows, but if the problem continues then that points to a hardware issue.