I'm not sure. It has to be set up right, you need the right cards down. In the meantime, it could be possible to kill treebeard and other such stuff. It's not invincible, not even once it's got all the stuff in place. They have to wait for regroup phase. So, assuming you can delay them until site 7( Which is reasonable), it's possible to get to site 9 first. It's also possible, due to treebeard's twilight cost, that somone may be able to swarm the turn treebeard is put down.