Operating System vendors provide free upgrades and security patches to keep our computers safe and functional during the support lifecycle. Some vendors announce the lifecycle ahead of time (see chart above), while others simply end support for old versions soon after each new release.
Without support your device gradually becomes less secure and less useful unless you can upgrade to a new OS version. Sometimes upgrading is not possible and you’re forced to replace a computer that isn’t broken.
To avoid troublesome upgrades or early obsolescence, always choose an operating system with a long planned support lifecycle. Windows 10 and CentOS Linux 7 will receive free security updates for the next 10 years.