[Dovecot] getting rid of old spam from +spam Maildir ?

I'm trying to setup per user '+spam' delivery from amavis tags, so that each user gets any mails tagged as spam to 'spam' Maildir via +spam Dovecot lmtp delivery.

after say 7 days I want to delete all spams older than 7 days, if I simply delete mail files from the file system, is that a 'bad thing' ?

what is a proper way to do that, and scripts ?

for removing/archiving old uncollected emails in main INBOX I use archivemail from sf, but, don't think I can do subfoldrs with archivemail

any pointers (and scripts) welcomed, thanks

-- Voytek