The answer for many individuals goes to be, as a result of one in every of them burned out. however there area unit valid reasons to alter bulbs that also work, particularly on older cars. For extremely previous vehicles, with incandescent seal beam bulbs, associate upgrade to grouping lights is perhaps a decent plan. Even for cars from the Nineteen Eighties and Nineteen Nineties, there area unit higher, brighter bulbs out there because of advances in chemistry and glass, thus associate upgrade could also be so as. Older bulbs place out less lightweight over time, however the amendment is thus gradual you’ll ne’er notice it; thus you’ll simply wish to place new bulbs in when five years of use.
Don’t forget, once a bulb goes out you risk being force over and ticketed by the police, though you’ll typically be a warning and many days to interchange the bulb (and prove you’ve done it). however it’s typically really easy to alter the bulb, why risk the hassle?