I'm not aware that there is any form of enforcement. Licenses are not "assigned" per say. The ePO server just reports based in the number of managed systems.
So, no not that I'm aware of. The licensing module is based on 180 days. To "de-assign a license", the system needs to be removed from ePO
So I could format the computer and remove that PC from ePO and I should be good?
sure, you just need to delete the system from ePO