There's a good chance that it's a coincidence. Since CF and LED bulbs have fallen off a cliff in price, the manufacturers have been cutting corners on the quality and tolerance of their internal components to maintain profitability and stay competitive on price. Premature failures have become pretty common.

One other possibility is a poor connection inside the ceramic socket causing arcing and heat. With the power off (open the circuit breaker to be sure), look inside that socket, where the bulb screws in, and check for any blackening or pitting of the metal contacts. Also look at the area where the wires enter the socket for similar effects.

A remote possibility contributing to premature bulb failures would be unusually high voltage on the circuit. In homes when this happens, it's usually caused by an improperly connected neutral. A telltale symptom of this problem is that when large appliances start, some lights in the house BRIGHTEN, while others dim. It's not abnormal for some lights to dim slightly when large appliances start, it's the brightening that indicates a problem.

Thank you, David. I'm going to hope your coincidence theory is correct. Both ceiling lights have worked well since they were installed in 2003. As you suggested, I looked inside the ceramic socket, and it looks brand new as far as I can tell.

I bought new LED bulbs today--a different brand--and just installed one. We shall see....

Is that a fixture where you could twang the bulb (or the holder). Vibration can be a killer and some fixtures will go through bulbs.

Hi, Ron--I'm not sure what you mean. Nothing comes in contact with the fixture; it's firmly attached to the ceiling. The room above it is empty most of the time, so no risk of vibration either. I'm glad you mentioned that though, as I have to do some work in that room over the winter, and this very old house has very little (sometimes nothing) between a floor and the ceiling below.

I'm talking about the bulb holder within the fixture not it's attachment to the structure.

Well, it has a heavy, translucent glass cover, so I'd say it's well protected.

Okay, here's a new clue: I just used my food processor, and ever time I pulsed it (turned it on), the light in this fixture dimmed. It didn't happen with its matching fixture on the ceiling a few feet away.

It didn't happen at all when the oven was started, nor did it happen when I turned on the dishwasher. So as an experiment I unplugged the food processor and plugged it into an outlet a few feet away, on another wall (at a right angle to the first outlet). I turned on the food processor, and this time the light didn't dim.

I hope this tells you something, though I can't imagine what it might be. Thank you!

Unless the dimming is quite pronounced, it's probably not significant. Since one does it and the other doesn't, either the lights are on different circuits, or the bulb in one is more sensitive to voltage changes than the other.

As I mentioned before, what you really want to watch out for is when lights BRIGHTEN when you turn on large loads.

Thanks, David. The dimming is quite pronounced; at first I thought the light went out completely. But it returns to normal brightness. The dimming is definitely new, so I don't know what changed. It's always a challenge to figure out my circuits, by the way. The breakers are marked, but not necessarily correctly. I think the mix-ups started when a second breaker box was added for the generator.

OK, that's not as it should be. It could indicate a poor connection in the circuit. BUT, if that's the case, and if the light is dimming radically when you start the food processor, I'd expect that the food processor would also barely work.

Before I say anything more, what kind of bulb do you have in that light now?

The bulb is a 60-watt equivalent LED.

Could the problem be the food processor? I just tried turning on my big KitchenAid mixer, plugged into the same outlet I used with the food processor when it caused the light to dim, and the light didn't react to the mixer. The mixer is labeled 300 watts; no wattage listed on the food processor.

To quote James Bond, Once is happenstance, twice circumstance, three times enemy action. Put in a new bulb and see how it goes.

Good quote, Rwiegand--thanks! The bulb I put in yesterday is doing very well. No events whatsoever as long as I don't plug the food processor into its old outlet and turn it on.

Sorry, the correct quote is "twice coincidence". From Goldfinger.

Well, that's weird, because I read it as "coincidence." I really doubt I remembered it from the movie.

Well, let us know if you get a failure there, and we'll try to help further.

I'm still betting on vibration. Both incandescent and CFs are pretty prone to such failure. It doesn't take a whole lot of perceptible vibration in the ceiling/floor to cause some fixtures to shake enough to damage the bulbs. LEDs should do a bit better in that regard.

Thanks, Ron. So you don't think there's any significance in the fact that the light dimmed only in response to the food processor, and only when the food processor was plugged into a certain outlet?

Dimming of lights is pretty common when you turn on larger loads. While incandescents will dim and CFs will perhaps flicker, they shouldn't really be damaged by that.

Now if the bulbs got BRIGHTER when the load was added, you'd have a sign of a bad neutral somewhere and that could cause problems.