keeping file_db_data reasonable

Hi,

I was looking at keeping the file_db_data directory at a reasonable size by ensuring that entries are removed in a timely fashion.

Am I right that lifetime of entries is determined by the "keep local copies for" setting of the individual (IMAP) folder in which the corresponding email lives but also by the refresh interval of that folder?

IOW, if I set my Trash/Bin to update only when I select it (which seems like a reasonable thing to do) and also to keep local copies only for the minimum amount of time (= 1 min), will cache entries ever be deleted for emails that I delete if I never refresh the Trash/Bin and let the server empty it?

IMHO, cache cleanup should be on a different clock than checking for new email (aka cache fill-up), but is that actually the case?

Also, how does one set the local copy lifetime for an entire account?

Thanks,
R.

PS: reminder: I'm on 4.14 .