Four to five years of updates depending upon which Chrome OS device you buy.

Link: www.google.com/intl/en/chrome/devices/eol.html

Chrome devices receive automatic updates regularly that improve and enhance the device and software on the device. However, advances in hardware and technology eventually make devices out-of-date, and as time goes by, we can no longer provide updates to leverage new OS features. This document provides advanced notice of the End of Life date for specific Google approved Chrome devices, and is currently applicable only to Chrome OS for Enterprise and Education customers.

General policy
  • When a device reaches End of Life (EOL), it means that the product model is considered obsolete and will no longer receive full support from Googleís Enterprise team. Additionally, Enterprise customers using devices that have passed their EOL date may find that they cannot manage their devices as expected using the administrator control panel or leverage new management features released.
  • Automatic software updates are not guaranteed on models which have passed their EOL date.
  • Google will provide advanced notice of a modelís EOL Date on this page as soon as it is launched, giving our customers time to make purchase decisions.
  • EOL dates may be pushed later than the initial date published, but will never be sooner than listed, which will be at least a minimum of 4 years from launch of the hardware
  • Models that have not reached their EOL date will continue to receive OS updates and function with the Enterprise management service
  • The End of Sale date is controlled by the OEM (manufacturer) of the device model and has no relation to modelís EOL date. Therefore, it will not be shown in the table.