New
#51
The basic thing is after a time things go wrong a classic sign of something overheating. Which you say does not happen running the iGPU.
You can still damage a GPU and shorten it's lifetime by too high a temperature for long periods of time within ratings. A lot of cards over run Graphics memory chips and the GPU. If those components are not specially selected then damage is more likely.
Like I said, underclock or under run at 50% GPU usage, or something and see what happens. That is just about all you can do.
Graphic Cards contain billions of components so there is no way of a user isolating the problem within that Card.
You would like to think you have not damaged it, sure, but that is just wishful thinking.