There is a lot of information over the Internet about how to do a backup copy of the Evernote notes by simply copying the files on the local disk. Unfortunately, it is connected with the need to do a manuall copy. This can be automated (using Windows task scheduler), but then we need to have a running computer.
Therefore, in order to fully automate the process I took the Evernote SDK for PHP and wrote a script that using the Evernote API retrieves all notes, puts them into folders (as notebooks) and stores them in separate text files And finally creates a ZIP archive.
All you need to do is to use a single php file with a cron and then we have a fully automated backup process for Evernote.
Code is available upon request.