Fetch package archives only when they are not cached locally

config.org

@@ -21,13 +21,20 @@
      (package-initialize)
    #+end_src
 
+   We also need to fetch the package archives from ELPA and MELPA,
+   unless they have already been fetched:
+
+   #+begin_src emacs-lisp
+     (unless package-archive-contents
+       (package-refresh-contents))
+   #+end_src
+
 ** =use-package=
    The rest of this config grabs packages via =use-package=, so that
    needs to be installed:
 
    #+begin_src emacs-lisp
      (when (not (package-installed-p 'use-package))
-       (package-refresh-contents)
        (package-install 'use-package))
    #+end_src