Anything you can add to a folder, you can add to a Keep-It archive. Instead it 'learns' on the fly how best to spot differences between revisions, and so how best to save space. Keep-It archives can contain any mixture of file and folder types. This makes archiving any project a snip. A folder is deemed to have changed when the items it contains change.
Folders also change when the number of items contained change.
Adding an item, deleting an item, or renaming an item, will all cause Keep-It to consider the folder changed. Keep-It's ability to archive folders provides a powerful means to archive projects. If you add a project's folder to an archive, Keep-It will look after every new item you add to, and delete from, the project. However, Keep-It archives are designed to be project, not disk, oriented. We regularly test Keep-It with 500MB archives.