I agree with that sentiment in general but even though I've seen systems in continuous operation for 15 years, I've never seen anything make it to 20. I wouldn't write something with the external expectation it never made it that far, but in practical terms, that's probably about as safe as it gets. Even like embedded medical devices expect to get restarted every now and again.

Just as an example the Voyager computers have been restarted and that's been almost 60 years.