Battery life and camera specifications dominate phone reviews, but the number that decides how long a device is genuinely usable is the support window. Once patches stop, known vulnerabilities stay open permanently, and banking or authentication apps eventually withdraw support for the operating system version.
Two different promises
Manufacturers usually publish two figures: how many major operating-system versions a device will receive, and how many years of security patches it will get. The second is the one that matters for safety, and it is often longer than the first. A device can be receiving patches while no longer getting new features — that is a perfectly reasonable state to be in.
The clock does not start when you buy it
Support periods generally run from the device's original release date, not your purchase date. A discounted handset two years into its cycle may have far less remaining support than the price suggests.
