we (maintenance) changed the code every 7 days.
What's the use of that? Only makes it harder for the crew to remember them and that in itself is dangerous in case of incapacitation! It's simply used as a way to open the cockpit door AFTER A CERTAIN DELAY. If a terrorist were to use it without prior intercom contact with the cockpit or without being on the galley cam, the cockpit crew would simply lock the door. The cockpit door code itself is not that important!