This was recently revealed in an interview with Pixel Vulture. According to Crystal Dynamics’ Mike Brinker who is also the game’s lead designer, he claims that even if you were to spend 20 hours, you won’t be able to see and do everything the game has to offer. If you want to explore every nook and cranny, expect to spend around 30-40 hours.
Brinker was quoted as saying, “Expect to spend around 30-40 hours getting everything done. This is gathering every weapons, ability and completing every side quest. It all comes down to how you want to play through the game. Running through the game will take you around 15 – 20 hours.”
He goes on to add that the game is larger than its predecessor. “In terms of scale, all our hub spaces, the areas that allow you to explore and choose your own way to play, have been increased by three time the size.” In the meantime, Rise of the Tomb Raider will be released on the 10th of November for the Xbox platform and is expected to make its way onto the PC and PS4 in 2016.