Unlike computer systems that need regular patches, the PLC controller often are standalone or in isolated networks. They often get neglected when it come to upgrade projects in the organization and their operational life is often stretched much beyond their ideal lifespan. It is not uncommon in plants to come across some systems that are more than 15 or more years old. What would be the ideal operational lifespan of such systems and can it be enforced in some ways like computers where new apps donot run on old systems.