Very good alternative to Cookie AutoDelete which is actively maintaned and updated, i use it because Firefox's exceptions to clear data on exit for sites does not work, also if you're reading the reviews because you think that this extension does not have a decent reputation, click on "Read more" from "About this extension" and you'll see a link to the source code.

Got this as a replacement for the extension "Cookie AutoDelete" which is no longer operational nor being maintained. It contains everything that Cookie AutoDelete had (as well as some new features) and works excellently.