You can also schedule Google Takeout, which gives you a nice .zip or .tgz with mbox files, in addition to all of your other Google information. I have it set to deliver one of these backups every two months automatically.
I decided to setup a key and backup via the api for gmail and gphoto. i should probably do drive as well...
This works for email and says it will let you upload to another account. https://github.com/jay0lee/got-your-back