I modified the plugin so that there is no time breakdown at all. I've added a variable to my URLs to exclude certain categories, and conceived a variable "limit" to control the number of posts that appear. In my particular case I'm not concerned with the number of days shown, though I am exploring ways to paginate the feed so that I can increase the number without weighing down individual pages.
Someone else has raised the question of limiting the feed not by number of posts, but by number of days, which I find very interesting. That thread is here. I'm pondering ways to achieve this...
You can see my usage in action here:
http://www.yooko.fr (right sidebar)
http://www.yooko.fr/actualites/ (full page)
The code for my modified version of the plugin can be found here (though I've since modified the date string to include UTF-8 compatibility).