With several 10s of thousands of messages (~70 GB) in my accounts, I also had issues with TB using tons of disk space even when set to not copy messages locally. The issue was TB's global search index. If you disable global search indexing in your config, then manually delete the global-messages-db.sqlite file, you can free up those 10+ GB.

My fix for most annoyances was to copy mail locally, and run dovecot locally on the same box as TB (TB doesn't support standard maildir). I also added a wrapper script that does a VACUUM on all the sqlite dbs in the profile when starting TB.

With the above, TB has worked well for me.

I didn't realize how many sqlite files there are, I ran "find . -name *.sqlite", I see Chrome related files, cookie files, a file related to storage? Time to look for a new email client which is sad to say after all these years.

I eventually had to switch off Thunderbird as well for similar reasons and just live with mutt. TB just really didn't perform well at all on large mailboxes (dozens of folders, thousands of messages per folder) without freezing the UI, gobbling gigabytes of ram, etc - it is obviously not targeted at my use case.

Disk space is as much as you have mail. If not, there is something wrong with your profile.

I have 15 GB of mail across 5 email accounts and Thunderbird is currently sitting at 350 MB RAM. Rarely crosses 500MB, I think.

I am encountering some freezes and occasional crashes which are annoying, but on linux there is nothing better.