Additional info from Sylvania:
http://www.sylvania.com/ConsumerProd...skedQuestions/
A) SYLVANIA recommends changing your headlights in pairs about once a year. The end of Daylight Savings Time in the fall results in earlier nightfall and more nighttime driving. It’s the perfect time to upgrade your headlights. Remember, when its time to change your clocks, it’s probably time to change your headlights.
A) The life of any halogen bulb will depend upon your vehicle type and how much you drive. However, all halogen headlights dim over time. That’s why we recommend replacing headlights in pairs about once a year, before they burn out.
SilverStar is a high performance halogen headlight that produces a whiter light that research has shown can improve driver visibility and reaction time. The benefits of increased light output and improved color quality can result in a shorter life for high performance headlights, compared to standard bulbs.