I have two wall lamps in a hall way, about 10 feet apart that have 100 watt incandescent bulbs that have never been changed since we moved into the house in December 1992. They get regular, if not “heavy” usage, on for awhile, off for awhile. They are G.E. bulbs and I’d be willing to sell them to the government to study if the price is right.
I really don’t have a clue why they have lasted so long.
I have two wall lamps in a hall way, about 10 feet apart that have 100 watt incandescent bulbs that have never been changed since we moved into the house in December 1992. They get regular, if not “heavy” usage, on for awhile, off for awhile. They are G.E. bulbs and I’d be willing to sell them to the government to study if the price is right. I really don’t have a clue why they have lasted so long.Mechanical shock and vibration greatly reduced because they're firmly attached to your house; can't move when they're on. That's one reason.
Lifetime of incandescents is strongly influenced by the temperature at which they operate; this in turn is strongly influenced by the voltage they "see" at their sockets. I don't remember the exact figures, but it's something like a 5% decrease in operating voltage increases lifetime by, like, a factor of 10. Of course, that 5% drop also decreases the "efficacy" of the bulb, where "efficacy" is defined (by G.E., anyway) as the amount of usable (that is visible) light emitted per watt of power input.
Those are two of the factors behind the "hundred year bulb" that burns at the Livermore Fire Station. It runs cool, and it's attached to the structure of the building.
Another is that it was built super well, before cost-cutting and efficincy considerations trimmed every milli-cent from the cost of a bulb.
I have two wall lamps in a hall way, about 10 feet apart that have 100 watt incandescent bulbs that have never been changed since we moved into the house in December 1992. They get regular, if not “heavy” usage, on for awhile, off for awhile. They are G.E. bulbs and I’d be willing to sell them to the government to study if the price is right. I really don’t have a clue why they have lasted so long.
Oh, I forgot to finish...
With regard to your hall lamps, there may be some reason why the particular circuit that supplies those two bulbs is loaded down just a bit more than usual (perhaps it's a long run from your fuse/breaker box), thereby reducing the voltage to those lamps just a bit. A reduction of just a couple of volts would be enough to substantially increase the lifetime of the bulbs.
Another factor (you may have heard of this one) is that incandescent bulb lifetime is affected by the number of times the lamp is turned on and off. Perhaps the hall lamps are just tuned on and off once a day. Or, if you live in a vast mansion, maybe they're never turned off. That'd be nice.
I had a similar thing happen with a dining room light in our previous house. Then it hit me that the fixture was on a dimmer. We never put it on dim, actually, but even full on, the bulb was slightly dimmed and this lengthened its life considerably. I had another brand of dimmer on a different light, but the bulbs in it burned out on a regular basis.
They used to sell (and maybe still do sell) little inserts to put in the bulb socket that cut the voltage a bit to lengthen bulb life. I wonder if your bulbs might those things in the sockets.