ChromeOS devices such as Chromebooks, Chromebox and Chromebase recieve automatic updates that keep your devices secure. It's Google's policy that these devices receive up to 10 years of security patches and updates. 

If you'd like to look up your ChromeOS devices update sycle you can do so by clicking here and looking for your devices make / model. It'll then tell you how long you can expect security updates for your device to help you make informed decisions!