For HPS, at 12/12, about a year is a good time to replace. This is the time that it will still output a high number of lumens per watt used. I've never used MH, but people I know generally also use them for about a year.
gainesvillegreen Reviewed by gainesvillegreen on . bulb life? i think this thread is in the right place. anyways what type of life do you get with mh and hps bulb? if they are getting weak will you notice it? also does wattage play a role in life expectancy in bulbs? Rating: 5