Downloading them via IMAP would take forever and isn't efficient. It's likely heavily throttled by Google as well. Grabbing the whole mailbox in one go is a goo

Downloading them via IMAP would take forever and isn't efficient. It's likely heavily throttled by Google as well. Grabbing the whole mailbox in one go is a good approach. Having to use Thunderbird to read them is unappealing, though. I'd install them on my own server and run an IMAP server to access them, so that they're available via any IMAP client (mobile, desktop, or a nice open-source web UI like Roundcube).