I have a three bulb light fixture that had worked fine since I installed it five months ago. About three weeks ago one bulb would only last about 3 of 4 days and than blow again. It's the same bulb each time, the other two are fine. Thanks for the help.

Turn off power. Check your wires and wire nuts in the ceiling and actually expose the wires and see if its still tight. Check the ground also. Check the inside socket of the actual light. Does that socket bulb flicker at all when its on. It could be its not happy with the ground neutral or hot. When the bulb/socket needs to work hard to get even flow of electric its hard on the bulb and wears out quicker. Kind of a slow short and arcing on the wire connections and it will burn that connection slowly like a welders arc but real slow The bulb struggles and wears it self out quick. If it's a bad ground this is also a issue there to balance what it needs to get easy power. Remember that bulb actually blinks 60 times ( 60 cycle a second A.C)a second. When that cycle is interrupted on a regular basis it stress the bulb and burns out quicker.
Hope this helped and have a nice Holiday!