Here is Assassin Creed Odyssey’s Full Story Length Revealed:
It took me 41 hours to finish the story. I ended up at Level 37 of 50. I listened to most dialogues but skipped some (especially in side quests). You have to do a lot of side quests to level up. There are huge level gaps between some story quests and side quests are the only good way to get XP. Besides, they also reveal locations to new Cultists so you have to do them anyway.
If you listen to all dialogues it’s easily 50 hours+. If you skip everything then you can maybe rush it in 30 hours. In those 41 hours I also uncovered the entire map and that alone took 5-6 hours!
You need roughly 1 hour per level-up (4-6 Quests). The quests scale with your character level and so do the enemies and areas. The game is absolutely massive and 100% completion will take 100 hours+. Getting to Level 50 will take around 50 hours without XP Boosters (which can be purchased with Helix Credits through microtransactions).
I didn’t have any XP Boosters and was constantly underleveled. So you can’t just rush through it, doing side activities is absolutely required to be in shape for the next story quest. Dialogue and Gameplay are evenly split, meaning half the time goes into talking with NPCs and the other half is doing their quests.
There are 9 Story Sequences in total. It’s worth noting that the game doesn’t stop there. There is a lot of endgame content such as world bosses and an arena. There are also lots of other chapters / story branches that are not necessarily needed for the main storyline but still count as their own chapters and can be done post-story. One of the most sumptuous singleplayer games in recent years!