Okay...here we go..... didnt really want to have to explain. but okay. If you Professionally reflowed the shitty solder that is a xbox 360 board the problem would reoccur again. To fix it to make it last a year you would have to not only reflow but reball every pin on the processors with better quality heat resistant solder. chances are that no one would go through that trouble to make a xbox 360 work again. Im interested now to see what was done.
Pretty easy fix and it worked great for me. Good luck to you, there are youtube videos galore to help you out. The first time I did it, I did not allow it to overheat and then cool, just the x-clamp and then closed it up and it did not work. After I went back and did that it worked just fine, so I recommend doing that step for sure.