jQuery's CDN and Far-Future Expire Headers

Question Why does content served from jQuery's CDN lack far-future expire headers? (or, "What am I doing wrong here?") Background I'm using jQuery and jQuery Mobile on a web project. To serve these scripts, I use jQuery's CDN, per their directions. However, I've noticed that these resources are served without far-future expires headers, which prevents browsers from being able to cache them intelligently. Although the jQuery servers will respond with `304 Not Modified`, that's not the same as an expire header the negates that request altogether. I realize the simple answer here is "because they don't" however, I'm wondering why they don't, and if there's some way I can serve this content, ideally from a CDN, with far-future expires headers. Thanks for your time. Examples jQuery CDN http://code.jquery.com/jquery-1.6.4.min.js Response: ``` HTTP/1.1 304 Not Modified Date: Wed, 16 May 2012 00:05:27 GMT ETag: "9e68e84-16615-6ad9bfc0+gzip" Last-Modified: Mon, 12 Sep 2011 22:55:03 GMT Server: ECS (dca/532A) Vary: Accept-Encoding X-Cache: HIT ``` Google CDN https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js Response: ``` HTTP/1.1 200 OK age:134505 cache-control:public, max-age=31536000 content-encoding:gzip content-length:32103 content-type:text/javascript; charset=UTF-8 date:Mon, 14 May 2012 10:45:15 GMT expires:Tue, 14 May 2013 10:45:15 GMT last-modified:Mon, 02 Apr 2012 18:24:28 GMT server:sffe status:200 OK vary:Accept-Encoding version:HTTP/1.1 x-content-type-options:nosniff x-xss-protection:1; mode=block ``` Note the far-future expires date in `expires:Tue, 14 May 2013 10:45:15 GMT` Solution I'm using Microsoft's CDN hosted version which features a 1 year expire date: http://ajax.aspnetcdn.com/ajax/jquery.mobile/1.1.0/jquery.mobile-1.1.0.min.js Full list of CDN hosted files. @zuul explained below why some CDN hosted items have longer expire headers than others. Thanks!