There was a big investigation in the servicing industry a few years ago, and I never heard the end of it, but when it was done most of the bulbs were either sodium some kind of normal fluorescent or similar, and the discussion was to replace them after x number of hours, or to wait till end of life and replace as and when. Then along came the led replacements and muddied the waters as some existing lamps can be merely upgraded, but others cannot, and now as I understand it in many areas there are laws on light pollution as well which has meant baffled lighting is now the order of the day, though evidence that this actually reduces light pollution is hard to come by. LEDs make this easier of cores as normally they emit light in only one direction. Brian
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7 years ago