dovecot - Apr 2018 - Virtual mailbox doesn't refresh without deleting indexes

Hello,

I have a virtual mailbox with the following dovecot-virtual file:

mdbox/*
-mdbox/Archive/*
-mdbox/Junk
-mdbox/Notes
  all younger 604800 not deleted

This works at first, but after messages are older than 7 days, they continue to
appear in this mailbox forever. Even if I close all IMAP clients and reconnect,
I can't get the mailbox to omit the older-than-7-days messages without
deleting its indexes.

I have other virtual mailboxes that update as expected, but I don't think
any of those are date-based. For example, this one "refreshes" as
I'd expect:

mdbox/*
-mdbox/Archive/*
-mdbox/Junk
  flagged

Am I doing something wrong with the first virtual mailbox I mentioned above?

I'm using dovecot 2.2.13 on Debian GNU/Linux.

Thanks!

--Bret