I also remember the "Rocketeer" pieces from the tour. I moved to the California Central Coast a couple years back and just recently discovered the film was shot near here. I drove over to a local airport a week or so ago and there it was: Bigelow (Big O) Aviation. The hanger is pretty impressive. Even more impressive: I assumed it was a "location;" instead, I found it was a set (we're talking MASSIVE timbers inside) that was originally placed well away from town, dismantled, and re-assembled as part of an air museum. I would guess it has been repainted as the Big O logo shows no fading.
Interest in "Rocketeer" memorabilia seems to have waned so I've made arrangements to donate my collection to the museum; the curator is excited because he was already wanting to pump-up the currently weak exhibit they have on the film. Too bad the diner, Bee Gee, and autogyro couldn't be brought out here but it would probably be cost prohibitive and there really isn't the staff to do any restoration anyway.
It is a shame that those sorts of props can't be maintained but you have to be realistic: They were never meant to have lasted and that makes them all that much harder to maintain. To have built them to last in the first place is counter productive because no one can justify the added expense of construction and transport (as they would undoubtedly weigh more), especially if the title in question tanks (and let's face it, while we all probably LOVE the "Rocketeer," it never really found it's audience).
I went on the Universal (CA) Tour a few months back and a good chunk of Whooville from "The Grinch" is still there. Now, I appreciate the effort that went into all the oddly-shaped custom buildings and vehicles, but guys, tear it down: It's covered in spray-on snow and after seven years in the elements, it just looks like crap. It's not cute. It's creepy.