Does Leopard not cache previews?

I agree, at least in theory, but I also picture several hundred thousand previews being created and cluttering up the drives, unless you prefixed each one with a period -- and if you delete the file, then there's extra overhead for Finder to delete the previews. How often would these previews be refreshed from the file contents?

There're a lot of problems with it that occur to me. Frankly, I'm happy with it working how it is now. A little slow, perhaps, but oh well.