Sandy Barrens
I don't believe golf courses "evolve" very well, actually. Bunkers break down, greens get smaller due to years of lax mowing, shot values change due to equipment "progress", labor saving watering systems completely alter the maintenance meld, TREES GROW IN AND ENCROACH (I don't like trees) and even harmless trees create problems with air circulation and light needed for good turf.
The best example I can think of to reverse this damage is National. About 10 years ago, they began a program to remove all the underbrush that had grown up, prune back trees around tees, fairways and greens and re-claim the original putting surfaces. What a difference! Merion has done much here, too (see below) and I hear Garden City and Winged Foot have also done some good stuff along these lines. I'm a fan of ANGC's ongoing work, as well.
Sorry, but I believe that man and Mother Nature conspire over time to cause golf courses to "over evolve". Any long term plan should include a "face lift" every 20 years or so, IMO.
FYI, Merion has done some wonderful stuff over the last 3 years (and continues to do so) that has been overshadowed by the criticism of the bunkers' altered look. Take it from me - Merion PLAYS way better than it did 10 years ago.
Pat Mucci:
As to Pine Valley, to my mind, new tee boxes that add 20-50 yards to a hole (especially at different angles) qualifies as "substantive change" to a hole's playability. I would point to the "Open tees" at Shinnecock as the leading example of that. Also, adding "alternate" greens that are used half the time and are, arguably, at least the equal of the original also qualifies. Finally, if you remember PVGC from pre-1978, the greens were MUCH less treacherous when they were kept at a lower "Stimp". Now the greens are so fast, it's scary. If that ain't substantive change..........
However, the great routing endures.