I played it for 48 hours straight.
I am on vacation this week, but my son started school so we weren't able to take off and go anywhere. I have been relaxing at home and picked this up on Tuesday and have been playing it practically nonstop since then. I didn't really rush through it, and it's been a lot of fun. My wife did kind of want it over with sooner rather than later due to the violence/scariness (some involving children) and profanity (lots of F bombs in the dialogue, which surprised me) and she didn't want the kids watching it, so I kind of went through it as quickly as possible without ruining the experience or skipping stuff.
On a normal schedule, this would have taken me a while to get through. If you want to get most of the achievements and experience all of the content, it will take even longer. This game has more of a plot and scripted story/backstory than most others, and the more you take the time to listen to all of the scattered tape recordings, etc., the more you will enjoy the experience. And by the time you get to the end, it's all spoiled--so do it right the first time and you will have a lot of fun.