An HMO licence generally lasts for a maximum period of 5 years. A Local Authority does reserve the right to grant a licence for a shorter period of time if it deems so necessary.
Furthermore, licences are not transferable and if you purchase a property that is already a licensed HMO, the new Landlord will need to apply for a new licence.
Every HMO property needs an individual licence so a person that owns and operates more than one HMO will need separate licences for each property.