Halogen bulbs and sealed beam headlights have very fine tungsten wire filaments inside that emit light when heated. Even under ideal conditions, the filament can break, leaving you in the dark. Vibration caused by driving over rough roads, potholes and bumps will reduce the filament lifespan.
Other causes of vibration may be due to a fault in your headlight structure. If the bulb is not securely mounted in the headlight assembly, it will vibrate, even under normal driving conditions. Insecure mounting may be the result of a bent bulb socket or headlight housing.
Similarly, if the headlight housing is not securely attached to your car, the entire housing, including the bulb and filament, will vibrate while you are driving, shortening the filament lifespan. Vibration of the headlight housing may occur even if it is tightly attached to your car if one or both of the front wheels are out of balance. If you feel a shimmy in your steering wheel, this could be a contributing cause of successive bulb failures.
When starting your vehicle, either by turning the key or pushing the start button, many vehicles will divert electrical power from any accessories that are on in order to deliver maximum power to the starter motor. If you turn your headlights on before starting your vehicle, the lights will turn off and then come back on when the engine starts. This rapid on-off-on cycle may shorten headlight bulb life.
Any signs of condensation inside the headlight housing may indicate that water is leaking into the housing. Water and electricity don’t mix and any condensation may cause a short circuit leading to failure. Also, any condensation coming in contact with a hot bulb may cause the bulb to break.