If your lighting system has been installed with proper attention to voltage, the rated life for the current bulb (Ushio Bulb #1001430) is approximately 10,000 hours. This is based on the manufacturers testing and is rated when 50% of the said bulbs fail.
Many factors may have an effect on a bulb lasting the rated life. Voltage is the #1 detail to pay attention to upon installation. We can help you troubleshoot your system if you believe that you are not achieving a satisfactory bulb life.