Enjoy it for 30 days from the date you first launch ExtendSim. Once you reach the end of that month – if you haven’t already purchased the product – that free Trial period will end. All the model files and blocks you created during that Trial period will still be yours, but ExtendSim will no longer launch on your system. However, you will still have access to the Activation dialog where you can purchase and/or activate ExtendSim.