Vibration can cause the problem, as can high voltage problems. You can also look closely at your choice of bulbs, choose the bulbs with the 130 volt rating, they will last longer.
I had a problem with bulbs I used in my garage coach lights. The vibrations from the opener caused frequent bulb loss. I know it wasn't high voltage because the same bulbs would last forever in the keyless lampholders installed inside the garage. I changed them to edison base flourscent (compact) and solved the problem.
