i had the same issue after an long time of playing.
In my case it was not the graphics but the sound.
I installed the latest graphic drivers (AMD/Raedon). I did not work.
I didn´t noticed, that i was playing without my extern speakers. I connected them again with my pc and it worked.
No crash. Tried it today once more. Without speakers-crash in the morning. With speakers connected an working – all fine.
I remembered, that i had similar issues with another game – Mount and Blade.
That´s why i tried this.
Maybe it works with your problem too.