Light bulbs 400 HPS

Question: Do HPS bulbs just "go" or do they fade? Never held on to a light this long and it seems to be sort of dullish in comparison to my newer one. She's 400 w.

bulbs will definitely start to loose lumens the longer that you keep running them.. i forget the exact ratio of lumes lost / hours used, but i think they recommend replacing them like every five grows or so .. somewhere around that time i think is a good time to replace them..
if you have a light meter, it's a great way to be able to compare what they put out new vs used..

its something like a 30% loss in lumen output too while it consumes the same power.I would replace a bulb at least every three grows if you veg with it, streach that out if you flower and veg seperate. I dont follow my own advice sometimes but i try to. Conversion bulbs will just die off but they still drop lumens too. keep in mind this is shit ive just read and noticed with loss of yeild, i have no light meter or anything to back up my words.

Did you find that the yields were rduced GREATLY? You may have enlightened me on something that tortured and crushed my dreams a while back and I couldnt figure WTF.