One of the common misunderstandings of agile is that it avoids any long-term planning in favor of only planning a few weeks out. What agile does not do is support highly detailed long term plans up front. Agile methodologies, like Scrum, focus on continual planning for the entire range of the project. Like the iterations on the project itself, agile continually returns to the assumptions of the plan and modifies it based on reality.One of the principles of Scrum is that the team commits to the amount of work they feel they can finish in small iterations of time called Sprints. These iterations are typically two to four weeks in duration. The results of the last Sprint will be used to potentially modify the goals and priorities of what will be worked during the next Sprint. This allows the goals of the project to "drift" a bit every few weeks. Ideally this drift is for the benefit of the game.