Pontiac Repair: Brake Problem, pontiac grand prix, pontiac dealer

Question
I have a 1996 Pontiac Grand Prix SE that has continued to have brake problems for about 2 years.  I constantly have grinding in the rear brakes that seems to go away for about 5000 miles when I get a brake job but then returns shortly after.  I have had several brake jobs from various shops including a Pontiac dealer.  I have also recently had the rear calipers replaced.  The problem still returned.  Recently my parking brake light has begun to flicker on/off while driving.  Could my parking brake be slipping on and causing my pads and rotors to wear down so quickly?  Any info would be greatly appreciated as I have had no luck with several local mechanics.

Answer
First I need some more info Jeremy. When the grinding noise returns, are the brakes physically worn out and metal to metal? Have you brought it back to the shops and did they manage to get the noise to subside again for even a little while? What is the majority of you driving type, highway or city? And as far as the light, I don't think it's coming on due to the switch at the ebrake pedal, I think you might be low on brake fluid. Get back to me with the answers to the above as it will greatly help me. Thanks :)