low beam headlights needs to changed every 3 to 5 months

I am the original owner of my Mazda 3. I purchased it in 2005 about a year after it was purchased approximately every 3 to 5 months low beam headlight either side need to be changed. The car now has just about 200,000 miles on it and runs excellent no other problems other than those damn headlights. I've changed the bulbs, the plastic harness that attaches the bulbs that usually is melted. Dealer has done same over the years. Nothing fixes this damn problem. Frustrating to say the least, but the car is probably mechanically the best and reliable car I've ever owned.