Your suggestion will break the game. It took me literally 1 second to think of the following:

- Attack someone in the beginning of the age.
- Be chainbait.
- When you need acres, recall the army back. Total attack time = 500 hours. You get hundreds of acres.

Another scenario:

- Your KD got waved.
- The attacking KD never recalled the troops.
- You enter into a war with another KD.
- The first KD suddenly recalled all their troops. Attack time = 500 hours. Your KD lost 80% of total acres. 5 people got PKed due to timezones.
- Turns out the two KDs are allies.