There are two kinds of licenses: perpetual and yearly.
This license is valid for a year.
On expiration, the appliance downgrades to a free Starter license. You can keep using the appliance and have access to all your data, but cannot use additional features not included in the Starter license. Moreover, you will not be able to add new users, link new devices, etc., if you have reached the Starter license limits.
This license never expires. You will always have access to the features for the chosen plan available right now, plus those introduced within one year. This license includes free access to subsequent product updates, but new features added after one year will be locked.