Many of the instanced missions and quests in SWG may only be entered under certain conditions, and, once entered, may not be re-entered until more time has passed. This period of time which must pass is called the lockout timer. Under the best of circumstances, you will enter an instance and the quest will succeed - in this case, the lockout timer is in place to keep you from re-entering the instance and farming whatever loot is dropped in the instance. Under the worst of circumstances, you leave the instance because you have been killed - in this case the lockout timer is a penalty placed upon you for being defeated.