What type of licensing does Esri offer?
Perpetual vs. Term: Perpetual licensing carries optional yearly maintenance that provides you with software updates, tech support, and ArcGIS Online access. If maintenance is not renewed, the software will remain licensed at the last version under maintenance. Term licensing is a subscription-based plan that will come with all the benefits of maintenance as long as you renew the subscription. The license will time-out if not renewed.
Click here for information regarding Named User, Single Use and Concurrent Use license enablement options for ArcGIS Desktop.