I'm just starting my first SS site and I am adapting the simple theme that comes with SS3. I want to replace the 4 require themecss calls with a single Requirements::combine_files call, to minimize the amount of requests on my live site.

It works when I add the following code to the Page_Controller init() method:

      // combine css files
      Requirements::combine_files(
         'all.css',
         array(
            THEMES_DIR . '/simple/css/reset.css',
            THEMES_DIR . '/simple/css/typography.css',
            THEMES_DIR . '/simple/css/form.css',
            THEMES_DIR . '/simple/css/layout.css',
         )
      );

However there is a note there that says:
      // Note: you should use SS template require tags inside your templates
      // instead of putting Requirements calls here. However these are
      // included so that our older themes still work

When I put the call directly in the Page.ss theme file however the site won't load.
As I want to make sure I'm future proofing my learning is there any guidance on how I have to change the call when putting it in Page.ss if this is possible? Thanks.