May be an overheat issue - the two troublesome light fittings may not have adequate space for the hot air to disperse - lamps run hotter and fail prematurely.
Check airspace above bad lights and compare to airspace of lamps that perform well.
Good luck...
Peccavi
January 2010
Not sure if your spotlights are mains ( 240v ) or low voltage. If they are low voltage its possible that maybe the transformer is faulty.
Are you sure that you are installing the correct bulb ?
Do the two bulbs blow together ( at the same time )?
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