Bad example. Do you know where the code NRT came from? The airport is in Narita. Narita did not take the code of the "old" Tokyo aitport. Another example of this would be GSW (Ft. Worth's old airport) closing when DFW opened. DFW was a brand new designator. A somewhat better example of your point might be DEN. Although the old DEN wasn't renamed. It just closed.