diff --git a/theme/image.php b/theme/image.php
index 350db3eaf6cce..2ec860dc1bd33 100644
--- a/theme/image.php
+++ b/theme/image.php
@@ -56,20 +56,31 @@
     $cacheimage = false;
     if (file_exists("$candidatelocation/$image.gif")) {
         $cacheimage = "$candidatelocation/$image.gif";
+        $ext = 'gif';
     } else if (file_exists("$candidatelocation/$image.png")) {
         $cacheimage = "$candidatelocation/$image.png";
+        $ext = 'png';
     } else if (file_exists("$candidatelocation/$image.jpg")) {
         $cacheimage = "$candidatelocation/$image.jpg";
+        $ext = 'jpg';
     } else if (file_exists("$candidatelocation/$image.jpeg")) {
         $cacheimage = "$candidatelocation/$image.jpeg";
+        $ext = 'jpeg';
     } else if (file_exists("$candidatelocation/$image.ico")) {
         $cacheimage = "$candidatelocation/$image.ico";
+        $ext = 'ico';
     }
     if ($cacheimage) {
         if (!empty($_SERVER['HTTP_IF_NONE_MATCH'])) {
             // we do not actually need to verify the etag value because our files
             // never change in cache because we increment the rev parameter
             header('HTTP/1.1 304 Not Modified');
+
+            $lifetime = 60*60*24*30; // 30 days
+            $mimetype = get_contenttype_from_ext($ext);
+            header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
+            header('Cache-Control: max-age='.$lifetime);
+            header('Content-Type: '.$mimetype);
             die;
         }
         send_cached_image($cacheimage, $rev);
@@ -125,14 +136,7 @@ function send_cached_image($imagepath, $rev) {
     $pathinfo = pathinfo($imagepath);
     $imagename = $pathinfo['filename'].'.'.$pathinfo['extension'];
 
-    switch($pathinfo['extension']) {
-        case 'gif'  : $mimetype = 'image/gif'; break;
-        case 'png'  : $mimetype = 'image/png'; break;
-        case 'jpg'  : $mimetype = 'image/jpeg'; break;
-        case 'jpeg' : $mimetype = 'image/jpeg'; break;
-        case 'ico'  : $mimetype = 'image/vnd.microsoft.icon'; break;
-        default: $mimetype = 'document/unknown';
-    }
+    $mimetype = get_contenttype_from_ext($pathinfo['extension']);
 
     header('Etag: '.md5("$rev/$imagepath"));
     header('Content-Disposition: inline; filename="'.$imagename.'"');
@@ -154,14 +158,7 @@ function send_uncached_image($imagepath) {
     $pathinfo = pathinfo($imagepath);
     $imagename = $pathinfo['filename'].'.'.$pathinfo['extension'];
 
-    switch($pathinfo['extension']) {
-        case 'gif'  : $mimetype = 'image/gif'; break;
-        case 'png'  : $mimetype = 'image/png'; break;
-        case 'jpg'  : $mimetype = 'image/jpeg'; break;
-        case 'jpeg' : $mimetype = 'image/jpeg'; break;
-        case 'ico'  : $mimetype = 'image/vnd.microsoft.icon'; break;
-        default: $mimetype = 'document/unknown';
-    }
+    $mimetype = get_contenttype_from_ext($pathinfo['extension']);
 
     header('Content-Disposition: inline; filename="'.$imagename.'"');
     header('Last-Modified: '. gmdate('D, d M Y H:i:s', time()) .' GMT');
@@ -178,4 +175,19 @@ function send_uncached_image($imagepath) {
 function image_not_found() {
     header('HTTP/1.0 404 not found');
     die('Image was not found, sorry.');
-}
\ No newline at end of file
+}
+
+function get_contenttype_from_ext($ext) {
+    switch ($ext) {
+        case 'gif':
+            return 'image/gif';
+        case 'png':
+            return 'image/png';
+        case 'jpg':
+        case 'jpeg':
+            return 'image/jpeg';
+        case 'ico':
+            return 'image/vnd.microsoft.icon';
+    }
+    return 'document/unknown';
+}
diff --git a/theme/javascript.php b/theme/javascript.php
index 5b29b5742a518..d5d0d55aa5e59 100644
--- a/theme/javascript.php
+++ b/theme/javascript.php
@@ -53,6 +53,10 @@
         // we do not actually need to verify the etag value because our files
         // never change in cache because we increment the rev parameter
         header('HTTP/1.1 304 Not Modified');
+        $lifetime = 60*60*24*30; // 30 days
+        header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
+        header('Cache-Control: max-age='.$lifetime);
+        header('Content-Type: application/javascript; charset=utf-8');
         die;
     }
     send_cached_js($candidate, $rev);
@@ -88,12 +92,13 @@
 // parameters to get the best performance.
 
 function send_cached_js($jspath) {
-    $lifetime = 60*60*24*20;
+    $lifetime = 60*60*24*30; // 30 days
 
     header('Content-Disposition: inline; filename="javascript.php"');
     header('Last-Modified: '. gmdate('D, d M Y H:i:s', filemtime($jspath)) .' GMT');
     header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
     header('Pragma: ');
+    header('Cache-Control: max-age='.$lifetime);
     header('Accept-Ranges: none');
     header('Content-Type: application/javascript; charset=utf-8');
     if (!min_enable_zlib_compression()) {
diff --git a/theme/styles.php b/theme/styles.php
index 67420df130b28..2a086262772b3 100644
--- a/theme/styles.php
+++ b/theme/styles.php
@@ -57,6 +57,10 @@
         // we do not actually need to verify the etag value because our files
         // never change in cache because we increment the rev parameter
         header('HTTP/1.1 304 Not Modified');
+        $lifetime = 60*60*24*30; // 30 days
+        header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
+        header('Cache-Control: max-age='.$lifetime);
+        header('Content-Type: text/css; charset=utf-8');
         die;
     }
     send_cached_css($candidatesheet, $rev);
@@ -116,7 +120,7 @@ function store_css(theme_config $theme, $csspath, $cssfiles) {
 }
 
 function send_ie_css($themename, $rev) {
-    $lifetime = 60*60*24*3;
+    $lifetime = 60*60*24*30; // 30 days
 
     $css = <<<EOF
 /** Unfortunately IE6/7 does not support more than 4096 selectors in one CSS file, which means we have to use some ugly hacks :-( **/
@@ -131,6 +135,7 @@ function send_ie_css($themename, $rev) {
     header('Last-Modified: '. gmdate('D, d M Y H:i:s', time()) .' GMT');
     header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
     header('Pragma: ');
+    header('Cache-Control: max-age='.$lifetime);
     header('Accept-Ranges: none');
     header('Content-Type: text/css; charset=utf-8');
     header('Content-Length: '.strlen($css));
@@ -140,12 +145,13 @@ function send_ie_css($themename, $rev) {
 }
 
 function send_cached_css($csspath, $rev) {
-    $lifetime = 60*60*24*20;
+    $lifetime = 60*60*24*30; // 30 days
 
     header('Content-Disposition: inline; filename="styles.php"');
     header('Last-Modified: '. gmdate('D, d M Y H:i:s', filemtime($csspath)) .' GMT');
     header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
     header('Pragma: ');
+    header('Cache-Control: max-age='.$lifetime);
     header('Accept-Ranges: none');
     header('Content-Type: text/css; charset=utf-8');
     if (!min_enable_zlib_compression()) {
diff --git a/theme/yui_combo.php b/theme/yui_combo.php
index 85c63b09448a9..f3dba345c90d0 100644
--- a/theme/yui_combo.php
+++ b/theme/yui_combo.php
@@ -45,6 +45,18 @@
     combo_not_found();
 }
 
+// if they are requesting a revision that's not -1, and they have supplied an
+// If-Modified-Since header, we can send back a 304 Not Modified since the
+// content never changes (the rev number is increased any time the content changes)
+if (!empty($_SERVER['HTTP_IF_NONE_MATCH']) || !empty($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
+    header('HTTP/1.1 304 Not Modified');
+    $lifetime = 60*60*24*30; // 30 days
+    header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
+    header('Cache-Control: max-age='.$lifetime);
+    header('Content-Type: '.$mimetype);
+    die;
+}
+
 $parts = explode('&', $parts);
 $cache = true;
 
@@ -124,13 +136,13 @@
  * @param string $mimetype
  */
 function combo_send_cached($content, $mimetype) {
-    $lifetime = 60*60*24*300; // 300 days === forever
+    $lifetime = 60*60*24*30; // 30 days
 
     header('Content-Disposition: inline; filename="combo"');
     header('Last-Modified: '. gmdate('D, d M Y H:i:s', time()) .' GMT');
     header('Expires: '. gmdate('D, d M Y H:i:s', time() + $lifetime) .' GMT');
     header('Pragma: ');
-    header('Cache-Control: max-age=315360000');
+    header('Cache-Control: max-age='.$lifetime);
     header('Accept-Ranges: none');
     header('Content-Type: '.$mimetype);
     if (!min_enable_zlib_compression()) {