I am assured by a mate who works for game that m$ will be able to check the age of the console from the serial number, and will repair it without question, or reciept.
Hope hes right , its only 13 months old and it really has hardly been used.
i got mine back in less than a week, but that was during the summer, maybe they will be a little slower due to this being a busy period, but it'll deffo be no more than 15 days either way :)
Its got the same serial number as the old console, but, its definatley new, inless they replaced the case aswell as all the flaps had fell off and it was scuffed on the top.