A major UK airline did a trial many years ago and concluded that it was repeated switching on and off that reduced lamp life. A year or so ago, I noted that a major Australasian airline keeps its landing lights on all the time, even on the ramp, at a very low power, presumably for the same reason.
Anyway, what's cheaper, a few lamps or the lives of all on board? KAL007 wasn't the first and won't be the last.