First time I lasted until day 26 when I was driven to a corner but didn't lose, gave up though, started over, same result only in day 15, this playthrough though I'm doing INCREDIBLY good! I went with the foolproof strategy of "go FULL offense", so now I have literally over 200 archers, a catapult and 2 paladins on each side and the even the boss Greedlings die before they even reach the wall!