6 bulbs in 4 weeks? That sounds like remarkably bad luck, are you sure it is the bulbs? Sounds like you might have other issues, dodgy contact somewhere? Are the bulbs definitely fried? Can you try them in another location to test?
After reading this thread I came very prepared with all the tools before i started the job. Drilled the hell out of the lens around the screw then at an angle underneath it. Not the tidiest of methods but got the job done after a bit of "gentle" persuasion. Then replaced with a decent set of leds as recommended further up. Very happy.
Fitted mine yesterday, my screws luckily wasn't locked up, i removed the light units, cleaned the lens's and refitted them but the contact ddin't work at first so i had to have a good play about until they worked.
LED Lights by Ste Topping, on Flickr