Some companies have a mimimum nuber of dead pixels befores they replace. Some vendors offer a warranty in whic if there are any dead pixels they will replace but they usually charge a fee for that.
i am using ASUS K42jc laptop. i noticed some "dead pixels" on the screen so go searching some tips on how to fix it. i followed the "rub the screen" method. lo and behold, nothing happened. so i turned off the laptop, the next day, the "dead pixels" became long crappy DIM pixels like 1cm by 2.5 inch. i tried using the print screen but the print screen showed a "fully fixed" screen.