Bulb life is 'questionable' at best. 1-1/2 to 2 months can equate to 1080-1440 hrs, if left 'on'. Switching on/off affects life, as do vibrations. Dimmers extend bulb life somewhat, as the ramping up, as opposed to the 'jolt' of full-on is 'gentler' on the filaments.Lastly, ....bulb brand and 'lot' can drive you crazy sometimes. 130 volt bulbs do last longer, lumens are a little less....

- Chris Tubbs (Pine Island, FL), 03/25/2017

Line to neutral voltage with different 120 volt loads on? There could be a faulty neutral connection at the transformer or downstream to the meter even.Type of lamps? If they are from a big box store, the quality could be suspect.Multi-wire circuit? A bad neutral connection between the panel and the end of the multiwire circuit (three wire cable using two hots and one neutral) could cause temporary higher voltage on one leg of the circuit.Are these fixtures located in the first floor ceiling of a two story house? The vibration from walking, high heel shoes, kids running etc. on the upper level of the house can be very hard on incandescent filaments and on compact fluorescent lamps.Last resort, if the homeowner is very frustrated, rent a power quality monitor for a month and install on one of the circuits in question.Good luck!Larry

- Bobbie Rodgers (Greenwater, WA), 03/25/2017

What is the voltage? Mine cruises in the 124v range and 120 v bulbs don't last very long. I use 130v bulbs when available and dimmers when they aren't (candelabra luminaires etc)

- Fred Ward (Holland, IL), 03/25/2017