The following comes from Ubisoft community dev, Zack Cooper...

I can honestly say that the amount of time will vary relatively dramatically based on how you approach a mission.

If you’re waiting for the opportune time to sneak, it’ll obviously take you longer than those who neutralize every enemy they see. …but then there’s always the fail-rate, right?

If you’re planning on going ultra-aggro… you may find that you’re dying more (and thus, need to restart more).

I don’t know if we’ve got a specific quote as far as the estimated playthough time… but I can say that we’ve crammed a LOT into the campaign (not to mention CO-OP or Spies vs. Mercs)

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