> > Yes they will work indefinitely. Why wouldn't they?
Because the computer clock advanced past a date which triggers bugs or limitations on some component, and it cannot be adjusted backwards without a full reinstall, or it's talking to networked services which expect the clock to be close enough to reality. It might be possible to fix with third-party updates, but that's no longer "without updates".
And if you need a reinstall, the online account requirement and/or activation servers being turned off might make it hard without third-party modifications. (It's been a long time since I last installed Windows anywhere, and that was before the online account requirement; how hard is it to install Windows on a completely offline computer nowadays?)