Just judging from the screen shots I'd think most battles will take 10-20 minutes. Also the video in the "Musket Volley" thread is of Bunker Hill and it was like 15 minutes. Considering there are significantly less cities on the World Map and less turns I think we'll see less armies marching around. Then again who knows? We haven't played a full campaign yet and until then we'll never get our answer. (Unless there's a DEMO)