That's kind of the point of the Long Now foundation. The point isn't building clocks, the point is that by building a clock which has a real chance of operating on such a timescale, you put yourself into a frame of mind where you start accounting for effects of your actions far into the future. The idea is to get you really, seriously thinking about how you are changing the world over the next million years.

Oh, sure. Like I said, I’m in favor of the the mindset—but Yucca Mountain less intellectual-idealism than Long Now, and if it’s improbable that a clock will last maybe ten thousand years, what are the odds a nuclear coffin will survive a million? I just don’t think it’s something even the (no doubt) highly-skilled engineers on the project can truly grasp.