Just wandered if anyone can shed any light (no pun intended) on the subject of premature light bulb failure. I did do a bit of digging a while ago and found a document listing many causes i.e. surges, vibration, overheating, etc. but wondered if anyone knows of any other reason's why some bulbs appear to last forever and others don't even make close to the manufacturer m.t.b.f. and if there is anything in particular you can check :-D The two examples I have both relate to light fittings with several bulbs. In one case 240V 5x40W GLS in a star shape, wooden fitting, on ceiling, each has own mini shade above bulb. In another house there is mini 240V G9 halogen 40W bulbs, ceiling 6xbulbs and 3 sets wall lights 2xbulbs, all in one room, all affected. I also have a strange example of a single bulb bathroom light rose where tungsten bulbs work fine but low energy bulbs last a fraction of the expected life, (after three bulbs I gave up and switched back to normal bulbs to save money ;-)). Could it be the frequency of use ? An extractor fan is also wired in this circuit.