Although HID burners will last a lot longer than normal Halogen bulbs, they will fail over time.
Other reasons for failures could be breakage due to a car crash, moisture or incorrect installation.
When you install the burner, please do not move the base in any direct other than in or out. We do see quite a few burners which are broken at base. (when you hold the base with one hand and put very light pressure on top of the lamp, you can wiggle the glass tube while the base is steady)