[CentOS] Is every CentOS release supported for 7 years?

Coming from Gentoo -> Debian I am to trying to understand the way
CentOS works. In Debian very little happens in stable releases and you
use apt-get update to apply security updates and apt-get dist-upgrade
for a major upgrade.

In CentOS there is an yum-security plugin which allows you to install
security updates only. If I understand correctly the preferred way
though is to do at least an yum upgrade every 6 months in order to
upgrade to a point release.