I think 8 - 12 hours. However from now on I'm only going to be getting FPS on my computer if I plan to play them online. Stuff like Killzone and Bulletstorm (which are good games) I probably won't be buying anymore, mainly because I play through the single player once and then never touch them again. I'm probably just going to hire those games, cause I can finish it in a day.
Do not go gentle into that good night, Old age should burn and rave at close of day;
against the dying of the light.