I have long argued against a fix single baseline in project planning. Plans need to be updated periodically to reflect changes in the project plan since a proposal and the onward progress measured against the latest version of the plan. This allows for a more fine tuned management and provokes a healthy revisit to the project plan at strategic points.
Fortunately this was adopted in EU R&D projects a few years back so that in Framework 6 and now 7 projects are required to produce a whole project overview plan and a rolling detailed 18month plan every year. I find this process very helpful. We are currently producing the 3rd “Description of Work (DoW)” for the EU4ALL project (http://www.eu4all-project.eu/). So at month 28 in project we are updating the detailed plan covering months 25-48 (I know this is not exactly a rolling 18month plan but that is how it was worked out with the project review timings and the fact that unusually the project has a 4 year duration). As the management team in the project we are now adding detail to the plan that would have been impossible to know at the start of the project but that are important for us to measure against from this point forward.
I would compare this situation to iterative development in an R&D cycle. Here we have: plan; measure against that plan; revise plan; measure against revised plan; repeat ad infinitum or until project end.
Academics often make poor project managers. I consider myself a good project manager who makes a poor academic!