We often hear that a business unit's and organization's mission is sacred. That is, not only do we need to understand our mission and constantly be in pursuit of it, but also, that mission is fixed. Based on what you have learned about strategy, do you think that a mission needs to be fixed and unchangeable or do you, on the other hand, believe that although it needs to last as long as possible, at some point, even missions must be reconsidered and revised? Please defend your position and give examples in history to support it.