The thing I hate about that 7 year figure for support is that it comes with so many hidden catches. First and foremost is that it starts from when the device first came out, so in order to get anywhere near that figure you have to buy a brand new device which may or may not have any trustworthy reviews at that point. And even after that they may not get new features added to ChromeOS. I had an early chromebook that Google had explicitly promised would be getting an update to run Android apps and the Google Play Store. Years passed, it ran out of it's support period, and it never happened.