Not being specific to this car,I have found that problems with continual bulb failure are due to poor connections and happy shopper bulbs.I not convinced that voltage is a problem as I have experimented by blowing bulbs with 24volts and they seem very resilient.So could it be a vibration problem?Have you checked the bulbs to see how they have failed.Has the filament burnt out or is the filament intact but detached from the support wires?Osram or Philips products are usually not an issue.