One main reason why Milestone meetings (and other decision meetings) take longer than planned or even fail is from my experience that they become working meetings to explain the Steering Committee / Decision makers the complete project.
With this they are no longer pure decision meetings. Read below how to solve this in your first decision making meeting.
To solve and avoid that:
I get in touch with every Steering Committee Member upfront: in separate meetings, during a coffee, lunch etc. I present them the main facts, written, oral doesn’t matter. I convince them on the main things I need their agreement on during the final meeting (e.g. Project Closure meetings).
There is no need to explain every last detail of what you are going to present. From my experience people just want to feel involved. They want to get the feeling that they have an influence. By giving them this feeling (and if necessary of course let them influence things!) they are in a positive mood concerning my project. I collect their concerns, comments and include them into the presentation.
I do that with every one of them. It is time consuming yes, but it is definitively worth it from my point of view. During the final meeting everybody know already what are the main points and give their agreement. I guarantee that your chances of closing such important meetings successfully are much much higher when you approach and prepare the people.
Try it and let me know your experience in the comments below. I’m really interested in seeing if this works for you as well.