I really dont get your logic here. The vehicle has a warranty for a reason to cover defects in parts and craftsmanship. The CPO warranty provided extended warranty to cover major failures after the original warranty has expired. If your out of warranty and its a common failure, but you are the original owner of the vehicle. Most of the times BMW will goodwill the repair for being a known issue. Other than that you are out of luck, the car's warranty does not last forever.

However in YOUR case, the entire tail lamp IS COVERED under CPO. The bulbs, sockets, wiring and connector is not. NOBODY here CARES that you have owned and driven blah blah blah for so many years. Did you even get a CCA discount with your $175 repair? I have posted a bulletin that clearly shows that a tail lamp repair is covered under CPO, this bulletin was released when E53 tail lamps were on inter-galactic backorder and that repairing the failed tail lamps were the approved solution until parts are back in stock. Now that they are in stock, the CPO dealership should have no issues with replacing the tail lamp, and out of your pocket is $50.