I think that for both Grand Lodge officers and local officers a year in the chair is not very long. Before you know what you're doing you are almost gone.
The positions are serious and important ones, much like being an officer in a company, and there you'd never see someone only sit for a year (unless they mess up of course).
The positive side of is if you get a poor master you only have to endure him a year, but I think that if we had people in the chairs 2-3 years you'd see more continuity and possibly also more projects getting completed.
I know in several countries in Europe the WM will sit for a term of 3-4 years, and GM's for even longer. They rely much more on their subordinate officers in order to do this of course, but in the long run I think it is beneficial for the craft.