My computer have been 3years and had play many game and nothing happens. Just recently my monitor screen when black when play games like League of Legends. When my screen when black my PC is still running as i can hear my in game sound as well as i could also talk to my teammates in voice call.
My PC is Asus G20 with gtx 970 and usually it get hot over time when i do a regular temperature check. Up to 80 degrees.