Ok, I just mentioned that about the bulb because surprisingly, not a lot of folks know about that. As for the bulbs blowing......it almost sounds like an issue I once had with a bad voltage regulator. It was allowing too much voltage (about 14.5 if I remember right) out and the car was blowing bulbs regularly.

Hopefully yours is just a small batch of bad bulbs. As was mentioned earlier, get a couple new ones and see how long they last and go from there.

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)