How does Customer session cookie removal work when customer is inactive for cookie lifetime?

The default cookie lifetime is set to 1 hour. If customer is inactive on the site, customer gets logged out automatically. Howdoes this process work?

A website can specify an Expires or Max-Age directive while setting a cookie to a browser.
The browser deletes the expired cookies.
So the expiration is handled by browsers, not by Magento.

Agreed, But Magento refreshes the cookie expire time every time a page gets refreshed. How does it get managed?