It is unlikely to be printed on the box, but every Chromebook has an "Auto Update Expiration (AUE) Date" after which the operating system is unsupported by Google.
This is actually not unusual as it happens with cellphones, Windows OS, Ubuntu Linux.... mmm maybe just not MacOS as you keep getting free updates. But unless you reformat your Chromebook at this point with trusty Linux, you can't easily just put some upgraded ChromeOS on it. So it is something to think about especially if you buy it say 1 year into its 3-year lifecycle.
What happens when the dreaded AUE date passes? This means there will be no more automatic software updates from Google, no technical support from Google, and "business and education customers... should not expect that they can manage their devices as expected using the Google Admin console".
Hopefully, Google finds some way of extending this easily more like MacOS works to something more usable like 5-7 years.
Google's little-known Auto Update Expiration D-Day leaves users bereft of auto software refreshes and more – here's how to check yours