Thank You DTLow, tardis, JMichaelTX, as this puts a real foundation of essential knowledge under the subject of making backups in Evernote. This knowledge increases the value of Evernote by making it possible to recover valuable notes in the event of loss. I would only add the mention of the history which is available in Premium, but if you don't need Premium features, as I do not, making systematic regular backups using BOTH methods that Evernote offers is an essential and complete prevention against the loss of often irreplaceable notes.
I add one other level, for reference notes, where I want absolute assurance of backup, I export a PDF, so I have the text in a form where I can format the result in a page layout program for hard-copy reference. This is important where I only need Evernote to 'gather' the information and where I need a hard copy print out formatted in the way I want for convenient reference (Note contents formatted in alphabetical order and in columns on a single page.) But this is for my specialized use.