User since 2004. Wow. Is there a way to export tens of thousands of emails from Gmail?
If you use multiple operating systems, or you want to use a high quality open source client, best choice is Thunderbird (this is what I use).
On Windows the default email client is Outlook.
On Mac, iPhone, iPad the default email client is named Mail.
All of the above email clients will save your emails from Gmail on your HDD.
Every email I've received in the last eight years is stored on my MacBook, indexed in Spotlight, backed up in Time Machine, and available for offline reading whenever I need it. If my Gmail account was suspended tomorrow it would be a nuisance, but I would not lose any data and could recover from it quickly enough.
I've found it very helpful.