Gmail is adding another feature, which will be rolling out over the next couple months. This one should give users a bit of peace of mind.
With Google Takeout, you will be able to export your Calendar (which is not a new feature) and your entire mailbox (or selectively via labels) for access later.
I’ve had quite a few people write in asking if there was a simple way to do this, and unfortunately at the time, there was not. So this is a fantastic solution! If you ever needed to close a Gmail account, you wouldn’t have to lose access to your messages.
Gmail says, “You can download all of your mail and calendars or choose a subset of labels and calendars. You can also download a single archive file for multiple products with a copy of your Gmail, Calendar, Google+, YouTube, Drive, and other Google data.”