Upwards to even 80 hours
Assassin's Creed IV it truly an open world experience. There's so much to do, a ton of things to explore, and it's all happening in a near seamless sandbox. I had to know just how long it would take a player to 100% the game, and as I feared, I don't have nowhere near the time to please my OCD nature with this one.
I asked Ashraf Ismail, director on Assassin's Creed IV, how long it would take and he told me that "one guy in the office actually did it two weeks ago for the first time. He got a 100% sync, which was mind blowing. This was one of our testers, so imagine he's a tester who knows the game really well. He's been working on the game for a year and a half. From zero to a hundred on one build [of the game], it took him 48/49 hours. The thing is, he knew what he was doing is the crazy part."
Nearly 50 hours for a guy who knows the game like the back of his hand. Wow. For the rest of us that are not as familiar with the game like this tester is, Ashraf estimates that it will take anywhere from 60 to 80 hours to get a 100% sync.
Don't worry though. For the core storyline, it will take you roughly 20 hours to complete that. Still, beyond the story there's all sorts of side missions, the whole open naval combat, all sorts of hidden things to find -- There's a lot, suffice to say. There's even a throwback to Altaïr's ultimate armor from Assassins' Creed II. You'll find a couple of ultimate-like armors that you'll want, and to get them you'll have a bunch of side activities to engage in.
So yeah, 50 to 80 hours. And that's not even factoring how much time you'll invest in the multiplayer, or even the free companion app for mobile devices.