I've played two games for roughly 3 hours each, and barely passed the half-way mark on the clock in the first game, am less than 50% full on the clock in the second game. These are on smaller maps, with a larger number of shards games could likely last many, many hours.
Throw in the fact that you can turn the clock back during some quests, and I think Frogboy is right on saying this is no quick game.
Keep in mind this game is (I think) trying to combat the 4X problem of a tedious mop-up endgame. And from what I've seen so far, Sorcerer King is a great solution to that problem.