First thing to make sure is, when you change the bulbs, are you touching the glass part of the bulb? If you do that it'll make them break due to the grease from your finger tips causing a temperature variation on the surface of the bulb. Only other thing I can suggest is perhaps theyre too powerful for the bulb holder and drawing too much current? That would tend to cause problems with the bulb holder and not the bulb itself, but im sure I had a similar problem with 100w "rally" bulbs from halfords and they kept blowing.