I agree they work as an externalised list of deadlines, with the added
feature of being able to associate dependant tasks on them. As a Programme
Manager, I would use them to highlight which deliverables are not going to be
met, and then manage which tasks have a dependency on them. This way I can
manage the interdependencies between projects. For this you'll need a couple
of things, probably an SRS report listing dependencies for each project and
"consuming projects", and whether the dependency is likely to be late. A
similiar thing can be done using filters in projects, to see which tasks will
not finish before the deliverable start date. So, agreed they can get "out
of sync", but it's a management process to make sure they reflect reality.
In a programme sense, this might occur once a week or once a month, but that
process needs to be built and managed.
As a Project manager, I would want to know 2 things, and I can get them both
out of project.
1. Which deliverables do I depend on, and show me a view of the ones which
have moved, and are scheduled to be delivered after my start date. If these
occur, I need to flag the issue higher up the chain as an issue.
2. Which deliverables and I responsible for, and show me if I'm going to
finish the tasks in time to deliver those. Again, if not, I need to manage
those tasks to get the project back on time.
There is no silver bullet here, its about visibility and process.