Forever. I'm happily using an original HP11 with no issues at all.
I bought it because I was spending most of my time in ssh/emacs and I wouldn't be too worried about losing a Chromebook. Three years later the joke's on me.
As others have noted, crouton is super and updates are seamless. I use it locally way more than I'd anticipated. IMO the standout feature is the keyboard.
Civility?