Interesting FT weekend piece on Cold War relics, asking the question, Should they be dismantled or preserved.
Reminds me of being in Berlin years ago and realizing how the city missed out on a huge tourist attraction in The Wall. Yes, exciting and fun to pull it all down, but a great big section should have been preserved for history and tourism.
So the simple answer is this: save enough for a critical mass effect on tourism and save the best ones for history's sake--whenever feasible. But err on the side of tourism, because if no one comes visit, then the money won't be there for preservation.