How long do lights last?

I bought a Hortilux 400W Super HPS on a digital ballast. How long does it last before it needs to be replaced? I have one 2 month cycle under it so far and just started the second.

Thanks!

I've heard: every 3 cycles; once a yr.; and, let them go til they burn out. I have a new bulb going next to one that's been through 5 or 6 cycles, and am not seeing much difference plant-wise. Not a definitive answer... but, I'd say that you can at least go another run or two (or more).

I don't have a whole lot of experience... but that's my $.02, FWIW.

Thanks a lot for the info.

change your bulbs like once a year if you use them heavy