I posted my heat testing results on DVXuser (mine was the camera that turned off without warning). Further testing yesterday with an external power supply and a cable battery adapter, and there's no difference in overheating. Again around 27 minutes in S35 and about 48 mins (with a 1min break at 29mins) in FF. I did notice that in S35 4K mode, that it did sometimes overheat without first getting a temperature warning icon. And testing with USB power wasn't enough to to keep the camera on.