On 02 Feb 2019, Paul wrote in
alt.comp.os.windows-10:

I have a copy of Windows 10 in a VM (where it would not have seen
a qualifying OS), and it just shows the watermark in the corner
every once in a while. I haven't noticed it do a spontaneous
reboot, like in the old days. I have a copy of expired Windows 7
that *does* reboot (it's an Enterprise SKU in a VM you can
download from Microsoft, that I run in VPC2007).

I have an unregistered copy of Win10 in a Virtualbox VM. It doesn't
do the reboot thing, and I don't think it ever will. As far as I can
tell it will run forever will most or all features working except
for any personalization - you can't change wallpaper or colors or
any of the visual customization stuff.