I have heard this happening ocasionally with aftermarket bulbs b/c most are cheaply made. But the stock bulbs blowing too? I would then think your seal is no good and mositure is indeed getting inside. Did you check to ensure that the back of the lamp is closed all the way? B/C I know it's really tight there. Also check all your connections to ensure there is no corrosion. Wouldn't hurt to replace the fuses as well. Best!