A very long time, replace when it burns out. or 10,000-30,000 hours, replace when measured light output is about %75 rated or the ends char up.
do i need to replace it with 250w or can i use 200w bulbs found some 200w cheaper than the kit i've just got, so if they need to be replaced i could buy the cheaper 200w one but will it work in a 250w setup? ive been using 400w HPS i know a 250w HPS bulb wouldnt work in my ballast but new to CFL i havent a clue
cfl are self ballest so you can use any in a e40 socket attached to mains only reason hps os spacific is its jot self balssat but uses a balast set to a certain wattage and ignitor