A couple more thoughts about light bulb failures.
In general, heat will reduce bulb reliability and a multi-bulb head will tend to run hotter than a single bulb head. Check to make sure you have good air circulation around the head and make sure any cooling vents are not obstructed.
Voltage spikes can cause catastrophic light bulb filament failure. High voltage (that exceeds the bulb's voltage rating) is also an enemy of filament reliability. Your line voltage may be too high and "dirty" as well. You can ask the electric power company to put a voltage monitor on the electrical service to your house.