So I went to the backups-folder in our Confluence server to trim out old backups, and noticed that the last backup was run on the morning of November 5th. So our Confluence hasn't backed itself up for a week!
I then went into the Admin panel to look at the scheduled jobs, in case someone had disabled the job without telling me about it. And I see this:

The instance was installed on August 14th (migrated from another host) and backups have run fine so far. I find several of these "Last execution" and "Next execution" dates worrysome. The "Back Up Confluence" task is running because I started it manually to see if I could provoke anything in the logs, but nothing so far.
Confluence Server v6.15.9 running on a CentOS 7 server.