How is an Non-Stock Item set to Obsolete?

In setting up Non-Stock Items the Item Master cannot be changed to "O" because of the Inventory Cost Level. What method is typically used to prevent the further use of a Non-Stock Item Master? This particular type of Non-Stock Item is used on a Sales Orders for fees, penalties, and design charges. I have just finished cleaning up the Item Location File (F41021), the Item Cost File (F4105), the Average Cost file (F41051), and the Item Branch records (F4102) so the items could be switched from Stock to Non-Stock. Of course the first item I pick for a test is