Buy Japanese ones instead?

Check your ground and look and test for variation or intermittent grounding. Bad ground will cause variations in voltage that can cause filament failure. Vibration is another cause but in your case I would check the grounding system. Move connections if possible to check for continuity. This was a major issue on cars and trucks that lost bulbs at a high rate. Spikes in voltage are also causes of failure and one reasonable cure is a zener Diode in line to bleed of excessive voltage to ground.

These bulbs look great. A direct conversion to LED, with the same socket.

thanks, a g.a from me

If the globes are burning out in short order I would look at the supply voltage, or that the fittings are too small for the size globe causing them to run too hot.

I would swap them out for equivalent LED types for 4 reasons. 1/ They draw much less current. 2/ They are not as sensitive to over voltage. 3/ They don't generate as much heat. 4/ They will outlast the incandescant globe by a significant margin.

Available from most reputable auto suppliers or online via ebay & alibaba et al.

When you tell us short life, just how short? A few nights, four months of fairly steady use, three years?

These types of bulbs last several years for me in a car, enduring vibration and temp extremes. I agree, there seems to be some trouble with your power supply.

i'm guessing 20 hours of running time. heat factors are'nt involved. i have the covers off because i'm always replacing them. the lights are inside the the camper, so they're not exposed to the weather.. the light fixtures are the size of a dome light, so i need a bulb appoximately the same size as an 1156.

"[the voltage seems stable at 12v]"

Obviously, it isn't. Better to regulate 12 V.

I don't think the voltage is necessarily at fault. You must consider that the three big lamp manufacturers have outsourced much of the incandescent lamp making to other countries. At one time, China had about 4000 lamp manufacturers. Is it possible that they all produced a high quality product? No, I don't think that is possible.

Lamp making is fairly complex even though it looks simple. A lot of things have to be just right or the quality suffers. When you consider how many other countries are involved in making lamps, there is no limit to the opportunity for poor quality.

the lamps are running off a good 120v/12v convertor.

thanks guys. all g.a. s'

Are the bulbs in the fixture horizontal or vertical? I have a Rockwood camper with the same 1156 lamps, with a horizontal orientation and have reasonably good lamp life. I have been thinking about LEDs but have concerns with light distribution in the camper.

Go to Home Depot or Lowes. There are under-counter lights that use 12 volt, 18-watt, Xenon bulbs that are VERY pleasant (easy on the eyes) that last a long, long time. I have been using this light in my office when working on the computer and they are wonderful. I have been using the same light for years now, same bulbs. If you are like most folks who get wicked eye strain from fluorescent, you will consider these a blessing. Halogens are harsh and hard on the eyes, not as bad as fluorescent, and if you try to read and such by LED lights, trust me, you will regret it. LED lights are worse than fluorescent.

I guess it could be a surge/overvoltage problem.

I had a problem with short lamp life - of hours rather than days.

I fitted a dimmer switch 3 years ago, adjusted to just below maximum, and the lamps have worked ever since.

This was in a 240 vac circuit with a tungsten lamp, but the idea might work at 12volts with a suitable dimmer for your type of lamp.

I would stay away from LED lights for now, unless you hear about a specific brand that has held up well. It seems LED's are being cheaply made and don't last anywhere nearly as long as they should. Plus, they are being wired in series, so if one fails, the whole light will fail, or a whole section of it does. Here's some choices for you:

http://www.buyheadlightbulbs.com/MTEC-Superwhite-1156-Bulbs-p/mt-227.htm

You could dim them down to make them last longer.

You may also want to look at "heavy-duty" bulbs made for trucks.

This is just a shot in the dark, but, I'm assuming it's a 110V to 12V AC to DC converter not an AC to AC one.

ur correct. i left out that that info. i sometimes assume.

I think you are looking for a #199 bulb. That should be the heavy duty equivalent to an 1156. By the way the 198 is the HD for an 1157. How ever the things that others have brought up about poor grounds and fluctuating voltage and voltage spikes need to be addressed too. Good Luck!