@Andrew Reid, is there any way you could rerun this test except take a jpeg every 10 minutes and then at a higher or lower temperature to see if the same timing to disabled video applies. I'm pretty sure you will get the same result, but it eliminates thermal heating being caused by taking photos or actual temperature. At that point it is merely about the camera being on for one hour. Also have you reached out to others who might be willing to see if they can replicate your results. I'm not saying that there was anything wrong with your experiment but third party corroboration is usually a sign that you are onto something.