By default Project-web Cache-Control max-age and Expires are set to 48 hours for PHP and HTML files and to 24 hours for i.e. CSS files.
I would like to suggest lowering the default cache time to 1 hour, regardless of the file type, so users of i.e. Firefox will see faster updates (without hitting the reload button).
I know that these values can be overridden in PHP for example using the header function.
It's just an suggestion, I could understand if you figured 48 hours is fine because of traffic or s.th..