2+ years on mine, nothing yet.
That saying though, probaly around 30-40 hrs use time, so as with most things, it's posible the more you beat it, the more prone to failing, bar random luck ofcourse.
Have to say though, i probaly won't buy into a console again if failer rates go on as being as acceptable as they are today. No fun knowing you've spent hundreds on software and it's at the mercy of a failer on the hardware with need to buy in again... when the will might not be there.