Let me start with my question and then I'll provide the context behind it:
**Is there a way for me to create a full local backup of my Gmail account (all received and sent emails) using a program like Thunderbird, while also using Apple Mail as my primary email client?** I'll explain the issue and my current set up next, which is inadequate.

I link my four different email accounts to one Gmail account, so I've already centralized all of my send and receive email functions to one location. It's not perfect, because anyone who emails one of those four accounts, gets a response from my gmail address. I'm fine with that.

I have a different problem. I use Apple Mail as my local client, which downloads from my centralized gmail email using a POP3 connection. I use POP3, because I want my gmail account to serve as a central backup account of all my email, whereas I actively manage and delete my downloaded emails within Apple Mail. This works well for me.

The issue is that I want to make a full local backup of all of my email in my centralized gmail account. The best approach to do that seems to be using Thunderbird with the "download all emails" setting enabled via my Gmail settings manager. The resulting problem for me is that if I want to back up my emails to Thunderbird, while emailing in Apple Mail, Apple Mail will start downloading all of my emails too, due to the POP3 setting change.

So, I'm trying to find a better solution and would appreciate your advice:
Option 1) Set up a new gmail account and then forward all of my incoming email from my centralized gmail account to that new gmail account. Sync that new gmail account with Thunderbird. I don't like this option, because I just want to manage one email account (i.e. The existing gmail account that I have).

Option 2) Use something like the Gmail backup program to do an independent download and backup. I'd prefer not to do this, because I have to give the program my gmail password. I know I already do that for Apple Mail and Thunderbird, but I feel comfortable with that risk. I don't feel comfortable with those little independent Gmail apps. Apple and Mozilla have too much to loose from maliciously appropriating my password.

Option 3) When I want to back up to Thunderbird, quit Apple Mail. Take the existing account linked to my Gmail address offline. Set up a new account in Thunderbird (because I will be performing an essentially brand new full backup) connected to the Gmail account. Switch my Gmail account settings for POP3 emails from "download recent emails" (which is what I want to use with Apple Mail) to "download all emails". Turn on sync-ing for the new account I just set up in Thunderbird, so that I get a fresh backup of all the emails. Wait for a night for the full sync to happen (if I'm lucky and other things don't get messed up). Delete the older account I used in Thunderbird for the previous backup (to save disk space). Switch my gmail account settings back to "download recent emails". Turn Apple Mail back on.

Option 4) This is where I look to you all for help.
Can I accomplish this backup function with two local clients running POP3 better?
My goal is to have a local backup of my whole Gmail that I can then backup to my local external disks and my cloud based storage. Using an additional computer or offsite storage would not solve this issue.

Thanks for your time and any suggestions.

My System:
Mac OS X
Version 10.6.6