Batman: Arkham City marketing manager Dax Ginn has said the main game will take up to eight hours to finish.
Ginn told Gamerzines, however, that it'll take up to a day to complete the Rocksteady actioner when branching off on other things.
"Our QA guys can straight-line it - so not doing any of the side missions and just sticking to the core narrative path - in about eight hours," he said.
"If you're exploring and trying new things, obviously that adds a lot to the experience and the game time. I would say for a normal player who knows their action-adventure games, between 20-24 hours."
Ginn added: "We don't want to make these huge games that take a huge chunk out of your life. We want to tell an amazing story that you can really enjoy and not feel like you've got to take six months off work in order to get through it."
Warner dated Arkham City last Friday for October 18 in the US and October 21 for PS3, 360 and PC.