This article will explain the differences between perpetual and subscription licenses.
Perpetual licenses are valid indefinitely. Updates and support are included for the first 12 months with the software assurance. If you renew the software assurance subscription, you will get a new license key which grants you support and software updates for another 12 months.
Subscription licenses are valid for 1 year. Updates and support are included in the purchase price.
The license will stop working if you do not renew the subscription.