I understand that, but it just seems too much. The attacker, when he decides to attack, already has his armies prepared. The defender has to react, mobilize, repel the invasion, and hold it for 24 months. During that whole time, each day the invader occupies your land adds up and doesn't go down. I don't know how much you get from winning battles, so it can be that you can defeat the invasion that way, but since land ownership seems to weight more for this specific WG, I don't know. Anyways, the testers should know weather or not this is too much and it's easy for me to change.
Numbers in diaries are just to give you an idea, so of course will change if we notice problems. I changed the tick speed for defenders earlier this week.