It stands to reason that the more often you use the various lights on your vehicle, the sooner you will have to replace them. If you always drive with your headlights on, for example, you can expect the bulbs to burn out sooner than if you only occasionally drive at night.
The type of bulb also is a factor. Halogen headlights, for example, aren't supposed to last as long as xenon high-intensity-discharge lights, though the latter are far more expensive. LEDs are said to last longer than either (and use less energy), but depending on the type and number required are more expensive than either halogen or high-intensity-discharge.
Sylvania, a major manufacturer of bulbs for automotive applications, says that the life of any bulb also depends on the amount of voltage a vehicle operates on. Some manufacturers have bumped up the voltage to handle all of the additional electrical loads on modern vehicles. The higher voltage can shorten a bulb's life. Frequently driving over rough, bumpy roads also can shorten halogen bulb life by damaging the filaments.
Though you may not notice, as bulbs age they don't generate as much light as when they were new. That means your headlights may still work after five or six years, but they may not be as bright or illuminate as much of the road as they used to. If you have to replace any bulb (or decide to before they burn out), check your owner's manual to see what bulb is called for. If you're a do-it-yourselfer, you should save money by replacing bulbs yourself. Information should be in your owner's manual on this. Some headlight bulbs are extremely difficult to get at, and you may have to remove a battery or reach the bulb through a wheel well, so check this out as well before you decide to do it yourself. You might be able to find helpful tips online from others who have done it.
When you shop for headlight bulbs, you will probably discover that several are available for your car at different prices based on claims of brighter, whiter, longer, etc. Read the fine print. Sylvania says its Silver Star bulbs are 35% to 50% brighter than standard halogens but "may have a shorter life span." The company says the average life of Silver Star bulbs is "approximately one year."Related