Looking at the backlog again, we turn it horizontal. It now has the shape of a Release Plan, fitting nicely into a calendar.

The plan will be subject to change after every iteration, and the detail of the plan is only high in the first (or next) one or two iterations at any time.

I like to work with two week iterations. You will get more frequent feed back from the users with short iterations.

Now you can book every iteration meeting for the whole project. The dates are not to be changed, even if the scope of the project does. The iteration meetings are held on time, and the work finished at end of each iteration is demoed.

The customer may change her mind about the solution, and the team and process must accommodate this, embracing the change, within the cost and schedule of the project. Of course, changing requirements demand re-prioritization and re-planning within the schedule.