Some people are happy to leave all their data on Google forever, but we’re of the opinion that leaving it there for too long, especially if it contains personal data, is risky. How strong is your Gmail password, for example? What if Google accidentally deletes your account?
Here’s an article from MacObserver that shows how to download your Google data using Google Takeout. Emailchemy can convert the email found in the Takeout folder to something you can import into an email app on your computer, like Outlook, Apple Mail, Thunderbird, etc.