well, I know it's not cause of the wiring job I did, cause I took my time and carefully soldered each connection. Both sides burn out too.

 

Hey guys I had problems with bulbs burning out too, most bulbs would last maybe 2 months tops. This is what I found is happening, when you start the car with the headlights on it creates a slight voltage spike to the headlights. I have actually verified this with a volt meter, I was getting tired of shelling out anywhere from 60-80$ for bulbs(always buy PIAA'S ). Just make sure that the headlight switch is off before starting car. I havent had to change the bulbs for over a year now