I have an idea that might solve the problem without too much additional verbiage.
Suppose we said that a successful verification of a course results in a new certificate, good for 10 years from the date of verification ride. So for a race that had a record set in its third year, and received a verification ride courtesy RRTC, they get an extra 10 on their lifespan. If it's a course that is expiring or has expired, the 10-year meter begins ticking from that year. The requirements would be the same as a verification, including distance agreement and adjustment to bring the course up to the required distance (that would cover a course that had a "hidden" change such as the new curbing Duane referred to - if the new measurement came up 3m short, the distance could be added a the start or finish, without requiring any additional rides).
Most of the time this ride would be performed by the original measurer, but it would not preclude someone else riding it. If it's the original measurer, the ride shouldn't take very long, given familiarity with the course - the main point of such a ride would be checking the landmarks (I wouldn't even bother calculating and relocating the intermediate split points, just ascertaining that a landmark for locating them was still in existence).
Not sure if we want to require that he/she be a certain level measurer or at least "experienced" to preclude the scenario Mark laid out.
This would seem to be a good compromise between simply taking someone's word that there has been no change and requiring a full from-scratch remeasurement.