Why would light bulbs go out after one month of use?

This could be because so many of the light bulbs are now so cheaply made they can't hold up to regular use. If this is a regular occurrence then you may have an electrical supply problem. In the United States the power coming into your home varies over time, but should be close to 120 volts. If it is too high or you are getting power spikes the only thing you may notice is burned-out light bulbs, but you may actually be shortening the life of some of your most expensive household appliances. Refrigerator and Air Conditioning compressors may burn out prematurely if the voltage is too high. Voltage fluctuations can also be caused by an improper ground on the circuit or coming into your house. Usually your power utility company will check your system out at no charge. Sometimes there may be a problem with the transformer on the line into your house. If there are no other problems, try using heavy duty light bulbs rated for 130 volts instead of the regular 115/120 volts. They have a heavier element that can take rough handling and power fluctuations better. You may have to get them at an electrical supply house. This is common problem in older homes. Keep in mind that the current in a circuit is the same throughout the circuit. Therefore if there is resistance in the wiring, that resistance increases the current through the bulb. <-- this is wrong The first answer above makes sense, the last sentence of the second answer does not. Reason is that the statement "Therefore if there is resistance in the wiring, that resistance increases the current through the bulb" is totally wrong. For any given mains supply voltage, any extra resistance put into a circuit will decrease the current in that circuit, which of course includes the bulb. If there is an extra-long wiring distance then you should use cable that is thicker than normal. That will keep the circuit resistance as low as possible. If you use too thin a cable for a long circuit run its resistance will be higher than it would be if a thicker cable were used. The thinner cable will "steal" more voltage from the light bulb (or whatever other device the cable is supplying) than a thicker cable will. This has at least 2 bad results: too thin a cable will get much hotter than it should (a possible fire risk) and the lamp will not burn brightly enough. In that case you might be tempted to try an even stronger wattage lamp, which will draw even more current through the thin cable, increasing the voltage dropped in the cable even more... (An even worse fire risk!) Another idea is: Use more Compact Fluorescent Lamps! See the related question: "What savings can a compact fluorescent lamp give?"