I think this is a great idea, however, the years would have to last longer than 4-6 mins, cuz there would always be a battle if the server was filled with people. A year could last a couple of hours for example, allowing you to move across the entire map within that year while not producing much more within that year. This would allow the game to continiue as before while a battle is on. And as I see it, these games would take endless time before being over, so it would be better not to end up conquering Europe with swords in the year 3000.