I regularly see stories of software that is at least 20 years old now, running multimillion dollar industrial systems that are expected to last for at least another 20 years before being retired (if even then). There will probably be no changes to that software in the interim, and it's possible that it can't be changed even if you wanted to, for various reasons.
As long as the computer is well-isolated, the biggest ongoing risk here is replacing old and failing PC components when necessary. But the same might be also be true of the industrial systems themselves.
As long as the computer is well-isolated, the biggest ongoing risk here is replacing old and failing PC components when necessary. But the same might be also be true of the industrial systems themselves.