The spy program, redpill Agent is still a once off payment and the license does not expire. After your account has been created you can download install modules and use the modules to install remotely and secretly as long as needed.
redpill has however made a change in the redpill Agent system in that you can no longer download new install modules if Ghost Protocol is not active.
When you purchase a new license, Ghost Protocol is included for 20 days. That is more than enough time to download a couple of install modules. Once downloaded you can use these modules as long as you want. The system will not allow you to download a new module if GP is not active.
In the past, you could have downloaded modules without GP. These modules would then just have been created without the Ghost Protocols. redpill no longer allow this because these modules (without GP) has a very high anti-virus detection rate.
To see why it might be needed to activate GP again, see our article Ghost Protocol Explained.