Roamy here. As much as it annoys me to link the New York Times, this article about the Smithsonian spacesuit collection is pretty good. I had the pleasure of meeting Ms. Young, the now-retired curator of the spacesuit collection, a few years ago. She is the author of Spacesuits: the Smithsonian National Air and Space Museum Collection, a book I highly recommend for space junkies like me.
She was very helpful in identifying some of the problems with the spacesuit materials – in particular the crumbling rubber and the polyvinyl chloride plastic that, over the decades, degraded into something truly foul-smelling. Because of different materials used, the older Mercury suits were in better shape than the Gemini suits. The Smithsonian collection also includes suits from the X-15 test program, but the article doesn’t mention whether those are part of the traveling exhibit.
In looking at designing space suits for long-term use on the moon, we had to remember that the spacesuits designed for Shuttle and International Space Station use are much heavier than the Apollo-era suits. The Apollo suits only had to last a few days, not for years of thermal cycling, radiation, and micrometeoroid hits, plus the added problem of lunar dust going where you don’t want it. A future astronaut has enough to worry about without having to climb into a funky-smelling suit.