Login to WHM and click on the "news" link, that will give you cpanel's latest news including when Easyapache updates, php updates etc have been released.
Updates for PHP and Apache happen fairly regularly, often every two weeks in PHP's case. If you have PHP installed on your server, I'd recommend that you run EasyApache as frequently as necessary to keep PHP up to date. If you do not keep PHP and Apache up to date, your server may have security vulnerabilities that could be avoided.