I don't want to jinx myself but it looks to me like Samsung are using a lot of software "hacks" to do thermal management and generally make up for some hardware design flaws with the Note 4 and people using custom ROMs (that probably don't have these limits) and/or using mods that remove other thermal limits like the camera ones are probably making up a significant number of the people seeing these failures due to more frequent thermal cycles and more extreme thermal cycles that are pushing the weaknesses with the phone's hardware.
Great to see folks with the phone still - may they serve you well! *touches wood*