Google offers a page with all the information you’d like to know about updating a Nexus device. However, recently, Google has updated this page with official information about when Nexus devices will cease to receive updates from Google.
Usually a Nexus device’s lifetime is around 2 years. For two years since their launches, these devices received updates directly from Google before most if not all manufactures can push out updates. (there was the strange case of the Verizon Moto X (2013) which received Kit Kat before the Neuxs 4).
Whether it’s a full version update (ex: 5.1.1 to 6.0) or an incremental one (ex: 6.0 to 6.0.1), Google will stop updating its Nexus devices according to the chart seen below. Strangely, though, the Motorola Nexus 6 is not in the chart. Perhaps the date of decay for ol’ Shamu has not yet been decided.
In case you’re wondering about Android’s monthly security patches, Google says Nexus devices will receive security updates “For the longer of 3 years from availability or 18 months when the Google Store last sold the device. For example, since the Google Store stopped selling the Nexus 9 in April of this year, it should keep getting security updates until October of 2017, 18 months later.
The current generation of Nexus phones, 5X and 6P, will be getting their last version update in September of 2017 while the Nexus 9 will cease to receive version updates in October of 2016.