I have a customer that lives in a large house with a rather large amount of recessed lights. The customer complained that her bulbs keep burning out about every 1.5 to 2 months. We've changed the bulbs on three occasions over the last 6 months.
We have inspected the metal contact tabs on a number of recessed lights and they seem fine. I've also changed her neutral bar since it was overloaded. Other then suggesting 130 volt bulbs are there any other areas we may be missing?
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.
The only time I have seen a similer problem was a stray voltage on the neutral due to a fault at another site. (Rusty nail replacing a consantly blowing fuse allowing back feed on the neutral) so insteadof getting 240V between live and neutral customer was getting 415V between live and neutral (and 240 between neutral and earth) needles to say the owner of the other site was prosocuted