Everyone that has warred enough has gotten caught at some point where your army gets home 2-3 minutes before a tick, and you have to do a mad scramble to make sure your troops are back out the door for one reason or another (overpop, ghosting horses, etc). With the fluidity of acres and peasants for attackers in war, you can't precisely control attack times to avoid this situation other than sitting with army home, which has it's own set of disadvantages. You're already fighting the enemy, why should you have to fight the clock as well?

I'd propose adding a +30 minute option to the war room to help alleviate some of the stress involved with getting your army stuck up against the tick. I see it as purely a tactical play, so it would have no gains modifier, and the disadvantage would be in being exposed to the enemy that much longer.