Hello again Mahmoud
What you describe for the voice and security licenses makes sense. Keep the following in mind:
RTU or Right to Use licenses are licenses that use the “honour system” that is, they will always function even if their evaluation period has expired. This follows Cisco’s traditional IOS licensing scheme where the license is not tied down to a serial number or UDI (Unique Device Identifier). This is why even after a reboot, the feature continues to function.
Evaluation licenses can be enabled, but they will expire after the evaluation period. The functionality will stop working after the evaluation period is over. As you state, the feature must be purchased in order to continue using it.
I hope this has been helpful!
Laz