What if your Google account was blocked tomorrow?

But I used Thunderbird for access, which was set up to make local copies.

When I was -- ahem -- fired, they soon said that I had something that was theirs. But I had given that something to another employee, who was now saying she had given it to me.

Although I no longer had access to the company Gmail account, I had my copy of the email thread where the other employee and I discussed the handoff of said thing from me to her.

And that was that.

If you use any Google or other company's service for something important, it's good/essential to make backups.