Management of change for a modification everyone calls temporary

A temporary modification is installed to keep production going. It works. Six months later it is still there, it has been through three shift teams, and the people running the plant have no memory of it being temporary. Management of change usually covers the installation well. The weak point is the expiry: who reviews the modification at the end of its stated life, what happens if they do nothing, and whether the drawings were ever updated to show it. How is a temporary change closed out on your site, and how many are open right now?