EDIT: I chated with a Dell guy and it appeared all of a sudden 0_o Anyway he said even if it did vanished for good it don't matter about that. It's what they have in the databases.
I was gettin' ready to drop some "F" bombs
You may want to check the fans. Do your fans constantly cycle on and off? After a year, I had about 1/4" of dust built up that slowed down my gaming. The problem ceased after a thorough internal cleaning.
Just try to be stern about it and don't let them push you back from it. Say that after 3 repairs in this short period you're still having problems and you cannot let your system stay in a downed state this long. Most likely if you get a good tech, you will get approved.