Responding to questions on Bethesda's blog, co-creative directors Harvey Smith and Raphael Colantonio said that "play-style matters a lot".
"Play-style matters a lot. Very direct players will probably get through the game in 12 or 14 hours. Explorers who eavesdrop a lot will take twice as long."
The developers also spoke about the game's magic system, revealing that there are six active powers, four passive powers and 40 bone charms, which can't be unlocked in one playthrough.
Dishonored follows a supernatural assassin driven by revenge after being wrongly accused of killing the empress he was once sworn to protect.
It will feature a flexible combat system, enabling players to use a combination of stealth tactics and direct attacks. The outcome of each mission is said to vary depending on choices made by the player.
Photo gallery - Dishonored screenshots:
Announced last year, Dishonored is developed by Dark Messiah of Might and Magic team Arkane Studios, which features Half-Life 2 artist Viktor Antonov.
The game will launch in North America on October 9 and in Europe on October 12.
> Digital Spy previews 'Dishonored': Assassinate targets in Bethesda's steampunk game
Watch a trailer for Dishonored below: