That's because marking off milestones is not progress. % Complete is
duration worked divided by duration required. Milestones have zero
duration. With no duration there is no work to measure. As long as they
are not all marked off as complete, duration worked is zero and the idea of
elapsed duration versus total required duration doesn't make any sense as
there are no durations to that can be measured and compared. But when they
are all complete, the summary is marked complete and the durations of its
subtasks cease to be a factor.
The fix is to realize that a list of milestones does not make a project
plan, it's only a spiffy to-do list with deadlines. The project plan is a
detailed description of the actual physical work that needs to be done to
achieve those milestones by the dates they need to be accomplished. Work
can be seen and can be measured and is the force that drives the project.
Try listing the activities in detail that the resources need to do and how
long it takes to do each thing. Then tracking the time you've spent on the
work against the you think it will take to do it and completion measures
will make sense.
