I've measured a bunch of courses that have expired or are soon expiring, and remeasured some of them last year.
I found I had very good agreement w/ the overall distance.
I also found that, unlike the major, all-or-none changes that Keith describes, there were several instances of landmark changes: a utility pole renumbered, a driveway relocated, houses repainted and/or renumbered, and this January found a road that had been completely renamed (sounds like something out of the old Soviet Union).
While I was a big opponent of expiring courses, I think they do need checking from time to time, for the aforementioned reasons.