Very Slow Thunderbird. Works for about 3 emails then seizes up completely.

Actually this is more an observation than a query, but I hope it's helpful. My Thunderbird V147.0 running two accounts on IMAP, Windows 11 and a lot of local folders (35Gb) had slowly got slower, but then just about packed up. e.g. 5 minutes to load one email, 20 minutes to download maybe 25 emails. Then it would stop completely requiring a Task Manager terminate and a restart. I read all the advice and tried a lot of it, but didn't see anything about the "global-messages-db.sqlite" file affecting performance. Anyway I got to having a look at it - 1.37Gb!! Deleted the "global-messages-db.sqlite" file and restarted. Thunderbird was back to normal and now 10 days later the sqlite file seems to be stable at approx 41Mb. I have no idea how it grew so big (33 times bigger than it seems it needs to be), I have never deleted it before and I have probably been using the current Thunderbird configuration for 20 years, but I imagined that reindexing etc would keep it a manageable size, clearly not. I wonder whether there should be a "Clear down Global Messages DB" button.