how long to people run their HID (HPS/MH) bulbs for before replacing them? manufacturers claim they should be replace after about 6 months of use, which i guess is just enough to squeeze two grows out of a bulb. is this really people experience of a bulbs life span? is it more economically sound to replace an ageing bulb rather than continue to pay for electricity to run it?
I hear you should replace it once a year. I let it go a year and a half before I bought my first replacement. Now I use the old one as a back up, and I plan on getting another after this new one is a year old.
If it's rated at say 10,000 hours... at 12/12 it's good for 800 days... at 18/6 it's good for 555 days. That's a long time... At least a couple of years... That's just my opinion.
That's the average length of time until full bulb failure. You get less light, but draw the same energy, once a bulb has passed it's prime. This depends on the manufacturer, but most start to drop off after 6 months or so. This doesn't mean you have to replace it right then, but you will be getting less light for the same energy costs if you don't.
