Keyless I’ve found the batteries ony last 12 months, so you’ve done well to get 18 months life.. I’ve just had my second battery replaced at second service FOC, first one was replaced at first service. But you should have had a repeated warning on the DIS, sure you didn’t just miss it? As others have said, you can always get in if battery fails by flipping the short section of the door handle off using key in slot just underneath, and then open old fashioned way.