It’s almost funny in a tragic sort of way how many project managers seems to think a project plan is a one-time event in the project. It isn’t. It is a continious task through out the project. As the project progresses, a bright project manager ajusts the plan so it fits the actual project progress. If the project plan isn’t updated, there might be selveral reasons. Updating the plan maybe causing a headace and take hours and hours. Keeping the plan up to date must be worth the effort, and if your project planning tool is easy to use and manage, then you just don’t do it.
There are several ways to cope with the need to ajust the plan continiously. Choosing tools that makes it easy to keep up with reality is a nice start. One strategy might be to look into my remember the milk as a PM tool recently posted on this site.
An other may be to drop the “master plan” with all information accumulated into one large document. Instead make a master plan, with only the top tasks and milestones - and keep seperate plans for all the top-level task. In the seperate plans, you only track the subtasks and with a “relative time scale” - so that once a fase is delayed only the starting date in the sub-plan changes not necesary all the subtasks dates and ressource allocations.