I posted something in I think 'open chat' is VLC whacky or what? Find that, maybe it helps. My monitor would stay on fine, according to my settings, for a few hours or a few days. Then all of a sudden it would turn off after 10 minutes. Every 10 minutes. Didn't matter if I was just at a desktop, on internet, playing video etc. Every suggestion I found across the entire world of the internet didn't cure it. I started paying attention to what I was doing just before it started and narrowed down the offender to VLC. Read that post, there are more details.
i5 3570k, ASRock z77 Extreme 4, 8 Gb Ripjaws 1600, Antec 430w psu, HVR 1600 tv tuner, custom case- marble top, oak face. Carver & DCM Time Window sound system. Mint 14 KDE.