Dr Ott claims the bulb will last 10,000 hours. I don't know. The ballast in my light did not last that long. Now, I find out that the ballast is not replaceable! Even though I am capable of re-wiring the lamp, Dr Ott's company refuses to sell me a replacement ballast. There is no place to get it repaired because no one can get the proper ballast from Dr. Ott. My expensive lamp is now just junk.