2004 KIA Optima Headlight/taillight Problems?

We've replaced several headlights and taillights on our vehicle already and they last not even 6 months. Dealer checked charging system and claims it is fine and that it's just time to change the bulb. But again and again? And the car is only 3 years old! I had one headlight burn out 6 days ago and today the ohther one went out and we just replaced both of them a few months ago. Any one else with this problem? Any suggestions? HELP!