I have had my Bosch oven (mdl HBL 3350UC) 10+ years. The oven Lens cover has broken three times, probably due to high heat used when baking bread. I have replace the lens -$30 each time.  I know use the oven with no cover and the bulb works fine.  I expected more from Bosch. This is poor engineering. When the cover explodes, glass gets into the food. But you are not aware of this, because there is no loud noise (or I am not sitting next to the oven when this occurs) Appliance Parts Pros and Sears are best prices. Amazon is $15 higher.