It's over three years old, and hasn't skipped a beat until the picture went out yesterday. What is funny is I was able to fix the picture by overheating the Xbox?!
What happens is the graphics chip gets hot enough to eventually warp the motherboard causing soldered pins to no longer be connected. You got it hot enough to melt the solder a bit and get a little bit of flow thus reconnecting the pins. I have never heard of this lasting very long usually less than a week never more than a month. There is a more permanent solution which involves taking apart your xbox and using washers to force the motherboard back into position, you can find videos of it on youtube.