If you use temporary licenses from MS technet you can examine, modify and extend (rearm) them using the slmgr command. Below are some of the commands that you can use.
You will need to execute these commands from an Admin command prompt.
slmgr.vbs /rearm ## renew your license
slmgr.vbs /dli ## View Activation, License, and Expiration Date Information i
slmgr.vbs /dlv ## Display detailed information such as the activation ID, installation ID, remaining rearm counts, etc.
slmgr.vbs /xpr ## License expiration date.
slmgr.vbs /upk ## remove production key
slmgr.vbs /ipk ###-###-## Replace the production key