Checking your Video cards temp is fairly easy on most Nvidia cards as such:
Before ShIII
After couple hours of SHIII
Some of you play SHIII with a lot of unnecessary background stuff and one of those is the 'Internet'. Shuting off the internet, virus checker, firewalls and a bunch of other background stuff will speed up your SHIII and give your computer a break. Also when graphics start getting goofy colors and pics being out of line ( streaked ) your graphic card is more than likely overheated as a lack of ventilating fans,lots of dust in computer, etc.
Like I said turn off the Internet when playing solo for your e-mail will still be there when your done playing.