Xbox 360 towel trick?

I recently got the rrod, but only one ring was red. I was told to wrap towels around it and let it over heat, and I did. It works right now It came back to life. But It will die again really soon? I placed a repair order and Im waiting for the box to come. If I send it in when it dies again, will they accept it? or is the warrany void since I tampered with it??