I was Defending Jerusalem with the Timer off as Egypt during the crusades. I decided that i should bring the fight to them. What i didn't know was that they didn't bring any siege equipment. So my choice was to run out and die or Quit without giving them losses. Being as lazy as i am i just put the game on 6.0x Speed and went to watch TV. I came back and they were still there. My Army was a little more then 10 archer militia and a couple Saracen spears. i was at a standoff with 4 crusading armies. As you can tell they wiped me out. Since then i battle with the timer on no matter what. After that the crusaders went on to attack my other towns and forts since only one could occupy Jerusalem.

Always put the battle Timer on. You can turn it off in game i believe(not sure pulling an all-nighter) for when you are sieging a settlement and etc.

Battle Timer: