As is the case with old bulbs in your house, the taillights can fail from time to time, particularly if they are older halogen bulbs. It is more common these days for taillights to be LED lights, since they are more durable and efficient. It is advised that you check your taillights as part of your regular vehicle inspections. They can go at any time and, because broken taillights are a safety hazard, the police may pull you over should they see a fault.