I'm not sure if I'm using the right terminology here, but I want to anchor my final milestone, so that when the dependencies change, the milestone actually doesn't move, but lights up in red.
At the moment, when the dependencies move, the last milestone moves along with it, showing that it will occur at a later time, like we have all the time in the world to launch our product.
Anchoring the last milestone, such as the launch date, it'll help us to see what our plan of record launch date is, and when the dependencies move, it'll help us to see that the launch date is at risk, and either the slip in the dependencies need to move back in or the launch date needs to officially move out (through the program review process).