Thunderbird provides an option per account - Synchronisation & Storage > Message Synchronising > Keep messages in all folders. I keep it unchecked for all IMAP

Thunderbird provides an option per account - Synchronisation & Storage > Message Synchronising > Keep messages in all folders. I keep it unchecked for all IMAP accounts. Only headers are fetched in the beginning, and rest is fetched when you open and attempt to view the e-mail. Sort of a middle-ground, and saves disk space.