As they are rated for 20,000 hours that pretty much says they are done after five flower runs.
12hrs/day x 63days = 3969hrs.
20,000hrs/3969hrs = 5 flower runs.
Arguments may be made that the light output degrades so badly after half the hours that the bulb needs replacement but I say BS.
When you're not growing tons of pot as a business the losses you may have from using older bulbs is not worth worrying about. My Chevy gets me from point A to B just as fast as a Cadillac but not as comfortably.
A quality bulb like Hortilux pays off in longevity and superior light output and the EYE True Blue works like a CMH bulb and does all phases of growth well.
You do get what you pay for so research the best bulbs for your grow then hunt down the best prices.