Index: wp-admin/includes/meta-boxes.php
===================================================================
--- wp-admin/includes/meta-boxes.php	(revision 18347)
+++ wp-admin/includes/meta-boxes.php	(working copy)
@@ -444,7 +444,23 @@
 ?>
 <input name="advanced_view" type="hidden" value="1" />
 <p class="meta-options">
-	<label for="comment_status" class="selectit"><input name="comment_status" type="checkbox" id="comment_status" value="open" <?php checked($post->comment_status, 'open'); ?> /> <?php _e( 'Allow comments.' ) ?></label><br />
+	<label for="comment_status" class="selectit"><input name="comment_status" type="checkbox" id="comment_status" value="open" <?php
+
+	$checked = false;
+	if ( $post->comment_status === 'open' )
+		$checked = true;
+
+	if ( get_option( 'close_comments_for_old_posts', false ) ) {
+		$last_allowed_time = current_time( 'timestamp', 1 ) - ( absint( get_option( 'close_comments_days_old', 0 ) ) * 24 * 60 * 60 ); // now - days in seconds
+		$post_timestamp = mysql2date( 'U', $post->post_date_gmt, false );
+		if ( $post_timestamp < $last_allowed_time ) {
+			$checked = false;
+			echo 'disabled="disabled" ';
+		}
+	}
+	if ( $checked )
+		echo 'checked="checked"';
+	?> /> <?php _e( 'Allow comments.' ) ?></label><br />
 	<label for="ping_status" class="selectit"><input name="ping_status" type="checkbox" id="ping_status" value="open" <?php checked($post->ping_status, 'open'); ?> /> <?php printf( __( 'Allow <a href="%s" target="_blank">trackbacks and pingbacks</a> on this page.' ), __( 'http://codex.wordpress.org/Introduction_to_Blogging#Managing_Comments' ) ); ?></label>
 	<?php do_action('post_comment_status_meta_box-options', $post); ?>
 </p>