Heat can be accumulated and can operate slowly on plastics. Heat has many origins. Materials have different resistances and reactions to the heating, heat can be transferred by conduction...

I could say you "****ing ******" (yes I could but these words are censured -_-') learn the difference between supposition and certitude, I have never been affirmative. :|
And you (we) don't know what they were doing with their device therefore, you can not state what sort of queerness they were doing, including abnormal overclocking, or other odd customizations.

"skin oils and/or UV/sunlight..." yep, I see, here, we do not use the same definition of the physics description of the heat. ^^ But indeed, we are talking about a pretty close phenomenon. Except for the peeling, it can't be only explained by UV exposure, the crazing affect the deep structure and is homogen on polymeric objects plus, it requires years of exposure, the photography shows some superficial/massive/accelerated and located damages. But skin oils and more generally dirty fingers are good candidates.

I have never spread fear, uncertainty or doubt about overclocking, and I perfectly now how it works and what are the possibles side effects. Don't be so enthusiast with that, if overclocking does revoke the warranty, that is for some reasons. That is not because your device easily support this one, that it will work for all.


PS: Slur was a sort of humor