Spooky games do not take that long to complete, more so because of the mechanics can get awfully tiring after a while, especially when there is no combat involved. Even saying that, Alien: Isolation had a perfect mix of hiding and combat, but it got slated because it was too long of a horror game. Frictional Games has always created games on the shorter side of things, and Amnesia: Rebirth is no different, so how long does it take to beat it?
How long to beat
Like most games, it depends on how well you can handle horror and how much you like to explore. That's not even taking into consideration how fast you are at puzzle solving, which is a massive part of Amnesia: Rebirth. Roughly it can take you around 6 to 12 hours to beat on average.
As we said, there are a lot of factors to consider. People who are not afraid and can breeze through the puzzles can easily complete the title in less than 6 hours, even more so if you ignore side areas and collecting collectibles such as notes and the like.
If you want to collect everything the game has to offer, as well as exploring everywhere, you're looking at easily 12 hours to do so. The notes over a deeper view into the lore of the game; even if you miss a lot of these, you can understand what's going on, but acquiring them will give you a more in-depth outlook of the game.
The puzzles are nothing to scoff at either, as some really can be quite tricky, and mixed with the atmosphere; it's understandable wanting to step away for a sanity check every once in a while. Amnesia: Rebirth offers no difficulty settings for anything, so all players are on the same level.
If you are playing through it casually, if you come across a note, happy days, if not no big deal, and you mosey on through it, it should take you how 7-10 hours give or take, which is a perfect length for a truly horrifying experience!