I had the same problem and it's the light fixture. LEDs (or actually their power electronics) can't stand nearly the same temperatures that incandescent lights

I had the same problem and it's the light fixture. LEDs (or actually their power electronics) can't stand nearly the same temperatures that incandescent lights can, so they get cooked. You'll notice brownish stuff coming out of the base when it happens. My fixture was a series of thick, donut-shaped aluminium rings connected via spacers forming a sphere around the bulb approximately the size of a melon. Three such spheres in total. The damn thing destroyed two whole sets of lights before I: -Disassembled one of the fixtures so that only the top is left, exposing the ceramic base. -Replaced the other two with "efficient mood lighting" 2W 2700K bulbs - those with a transparent head mimicking a glass bulb. It's not particularly beautiful, but hadn't had any problems since.