Functionality from End Dating an Operating Unit (OU)

Does anyone know the functionality or impact of end dating an Organization which is solely an Operating Unit (OU) in R12?

When I end dated an organization, I assumed -- incorrectly -- that AP users would no longer be able to enter invoices and process payments in the OU.  But they still can enter invoices now in October, even though I end-dated the organization in late September with a 26-SEP-2012 end date.

So my next solution was to go back to the Organizations setup form; query up the end-dated organization, and uncheck the Enabled checkbox for "Operating Unit" in the Organization Classifications section.  This is not a viable solution, because my AP users could no longer query up historical transactions (AP invoices; payments, etc.) for the OU after I unchecked that Enabled box.