A bit late to all this. I've just finished my PPL and wanted to share my experience in this regard. The Flying School that saw me through my training has many planes, each of which has a dedicated, charged iPad. On a cross-country recently, the iPad overheated mid-flight and shut down. It was a very hot day and had been lying on the seat. Trouble is, this had also been running PilotAware. So, suddenly and WITHOUT WARNING, that key source of information was lost. Fortunately, my personal Android tablet (Samsung), positioned right alongside, carried on doing its thing. My Android phone, on a suction thing in the windscreen, carried on doing its thing. I was actually navigating using a CAA chart with the route plotted, but I am glad I wasn't reliant on the iPad.
When I landed back at base and reported the issue with the iPad, I was told they'd seen this issue, albeit rarely, on other iPads on the fleet.