One step further, Have all your devices ship with all the features available. Let them run that way until they go past 60 days. If the device reloads it comes up in a basic license and most of the features that run their business stop working. That is unless the customer puts a License server on their network and loads a specific licenses prior to this happening. The next big pain is doing an RMA and transferring the license. Now imagine you have thousands of devices. I work for such a company and love the look on an engineers face when you try to convince them this is for the better good.