In my experience with renewals, the RD did not have a copy of the certified map or even know where to go get it. My conclusion from this observation is that the RD is not checking course layout with the certified map in hand from year to year to verify that nothing has changed. An expiration date forces the examination between map and the physical course. It's a verification that all is well. In the majority of cases re-measurement of an existing course is not particularly time consuming. The course layout is already there, the measurer just has to go ride it. If nothing has changed, there's not even a need to draw a new map which for me takes significantly longer than the actual measurement.