Well let me see: I manage all cities at the beginning of a turn. Then I move characters. Next I fight battles but I auto resolve all sieges if i besiege a city/castle. My last duty is to train new units. So on average I think that turns don't last that long.

Since a lot of field battles are against veteran siege engines accompanied by hardened peasants/town militia's they don't last that long.

The only time when a turn would take some time is when I am besieged or when I fight a nice field battle.

edit: I voted 2