I'd say good for 1 year.
Bro You the answer man .. You ever type more than one sentence ? I passed out at least 5 reps and still cant get you damn whats up with that ?
so how long do a 400watts hps last 12/12 for about 8 month now.
What I meant to say is ...... The bulb may last for 2 or 3 or 4 years......but it's "effectiveness" goes down after about a year.......
I change mine yearly.....
I'm a man of few words....
You get a "daily allowance" of rep love......use it all up daily..(if ya can)....then a few days later....it should let you rep me.......