One thing that I think will help make the battles last a more historic period of time is to stop ground combat at night. To use the "This is a Grand Strategy Game" arguement, while a few units in a division may undertake night combat for the most part night time was when units did things like sleep, resupply, move artillary around etc.
You should be able to start an attack at night (with the penalties that exist) but come the next night the battle on both sides should stop (each should recover some org etc assume they are in supply). Troops cannot fight (or for that matter march) 24 hours a day for days on end without becoming exhausted.
Obviously air and sea combat are not stopped but it would make a lot of sense to stop the ground combat.
You should be able to start an attack at night (with the penalties that exist) but come the next night the battle on both sides should stop (each should recover some org etc assume they are in supply). Troops cannot fight (or for that matter march) 24 hours a day for days on end without becoming exhausted.
Obviously air and sea combat are not stopped but it would make a lot of sense to stop the ground combat.