Since LEPTON 3.0.2 we modified get_page_headers and footers process.
The modified process will now check, if css-files or js-files are already loaded and prevent double loading.
This is almost important for js-files to prevent code misbehaviour on your site.
And at least it makes working for authors much easier for they didn't have to look for other addons.
Please have a look at the semantic template or algos theme if you want an example how to use it.