Though Apple didn't formally test the life span of the Apple Scanner bulb, only a rough estimate as to how long they are likely to last is possible.
We specify that the Apple Scanner bulbs supplied to us by vendors last a minimum of 200 hours of continuous use at an elevated temperature of 40 degrees Centigrade. Our experience using the Apple Scanner shows that all bulbs that stopped working had been in use longer than 230 hours at elevated temperatures of 48 degrees Centigrade. This translates into a possible life span of approximately 2400 scans. The actual life span of bulbs in a user environment might be a bit longer, but we are unable to establish any life span with specific test data at this time.