We expect that the purchased personal devices matching the posted specifications should last students for four years.
The care taken with the device will greatly impact the life expectancy.
A waterproof, protective case can increase the life expectancy.
Google has published the end of life software support (on Chrome OS) for all Chromebooks. If you plan on purchasing a Chromebook please review the following: https://www.google.com/chrome/devices/eol.html