Design flaw? Browser won't see updated content?

This module suggests that the "Browser and proxy cache maximum age" be set to a larger value - even an year. This setting is the same used by the web browsers, isn't it? So if a visitor checks a page and then visits the same page after sometime during which updates might have occurred, s/he might not receive the updated version since the web browser will not even contact the caching server until the browser cache expires.

What is needed is a way to set that value to something like 15 minutes or so, but get the external caching servers linked to cache the content for months or more.

I would ideally like the modules like Advanced Page Expiration → be used to control the browser cache time, but use the purge module to purge the content in the external caching servers.

Personally, I use Varnish. I wonder how to accomplish what I want.

I could not find details about how to get the envisioned setup configured. Or else, is the purge module limited to get the updated content only to the new browser clients, but not the previously accessed ones.

Or else, have I understood something incorrectly?

Kamal