about midway thru a second grow on the same 400 watt HPS, I stuck in a new one, was MUCH brighter ... otherwise, no noticeable flaws ... you get used to looking at it, and don't notice it's brightness has dropped ... I now put a new lamp in, every grow ... I use cheap $12 lamps, and see NO difference over my previous $80 Hortilux lamps ... Google ' 1000 bulbs ', outstanding place to buy bulbs, etc (in Texas) ... :thumbsup: