Clients who buy licenses with no expiration date. If you are a subscriber client, you will see the following text in the Licenses section in the Status window: "Valid until: Permanent". You will not have to worry about your license expiring.
Clients whose licenses have an expiration date. If you are a non-subscriber client, you will see the following text in the Licenses section in the Status window: "Valid until: 00/00/0000 ".