OK So the Expires header is set to 15 minutes in the future. I think this is the secret sauce. I've never seen this before but I plan on trying it out heavily in the future. You don't even need to wait for a 304 content not modified, there's simply no request at all. So cool!
edit: It seems like Expires is a bit older than cache-control, so not as relevant as I thought. I'm not seeing the 365 day cache control header you listed, it's anywhere from 5 minutes to 30 minutes.
It's just weird to see a browser totally trust a cache and not even verify using "etag" or otherwise. I'll probably have to do a lot of trial and error to get this to happen but I really like it, because it feels so fast.