As with their failure to find a cure for the common cold, experts have yet to produce a light bulb that will last indefinitely. We, thus, find ourselves on chairs or stepladders, more often than we would prefer, replacing them.

In addition to buying light bulbs designed for long life, there are other important factors that you should be aware of that will lengthen the life of a light bulb.

First, allow us to shed a bit of light on what it is that makes a light bulb shed light. In a word, it is electricity. Electricity heats a metal filament contained in the light bulb causing it to glow and give off light. Some of the filament, often made of tungsten, evaporates during use, due to the high temperatures at which it is operated.

The filament does not evaporate evenly. Therefore, some spots will experience greater evaporation and, consequently, will become thinner than the rest of the filament. It is at these thin spots that the filament will break, rendering the bulb powerless. Often this will occur when flicking a switch to turn on a light. The sudden rush of heat is just enough to turn the thin spot in the filament into a break.

How long should the average incandescent light bulb last? Although the figure varies by size and brand, the average maximum life is about 1,000 hours. That is about three months when operated 10 hours a day. A light bulb that burns around the clock will last about a month.

Many people believe that the ratings supplied by bulb manufacturers are anything but realistic due because their light bulbs rarely last 1,000 hours. Often, a light bulb with a short life is more the victim of conditions surrounding its use than of the quality of its components.

For example, excessive heat is a major cause of bulb failure. Excessive heat can be caused by several factors including a placing bulb with high wattage in too small an enclosed fixture. The heat can't escape; thus the bulb burns too hot, leading to short life. If you find yourself constantly replacing light bulbs in your recess light fixtures, it likely is due to overheating.

This overheating generally is the result of using a bulb that has greater than the maximum recommended wattage, or from insulation installed too close to the housing in the attic. This condition restricts adequate ventilation, causing the bulb to burn hotter.

Modern recess fixtures come equipped with a built-in circuit breaker that will automatically turn the fixture off when it overheats. If this condition occurs frequently, the bulb size and insulation should be checked. Some recess cans are encased in a protective housing that permits them to be covered by insulation. With others, the insulation is held back (typically 3 inches) in accordance with the directions.

Vibration is another frequent cause of bulb failure. Bulbs located under a stairwell, mounted on the ceiling below a second floor teeming with youngsters, attached to a wobbly decorative ceiling paddle fan, near an exterior door that is often slammed or attached to an automatic garage-door opener often are subject to early demise.

One of the most effective means of dealing with vibration is the installation of shock-resistant or rough-service light bulbs. These bulbs are a bit pricier because the filaments are sturdier, but are cheaper in the long run.

Another possible reason for early and frequent bulb failure is over-voltage _ when the voltage is 125 volts or higher. If you suspect that this is the problem, you can test for it using an inexpensive multimeter purchased from your local electronics store. If after testing, the voltage is indeed 125 volts or greater, advise your power company. If the condition is deemed safe, you can buy special 125-volt or 130-volt bulbs, although they are hard to find and are costly.

Intermittent electrical contact can cause flickering. This condition occurs when the bulb isn't screwed in properly or the contact at the base of the socket needs to be pried up a tad. In addition, the light socket can be defective, or there might be a poor electrical connection somewhere in the wires leading to the light - most likely at the fixture.

Flickering can do more harm than merely fraying your nerves. It can cause a fire. If it persists, have a qualified electrician check it out.