With the Garmin interface I think you can de-register your old GPS unit and register your new one, and change your plane identity too if you want. Ultimately, it does not matter to do this if you are programming the same type of unit because all the app knows is that you are programming a data card for a particular type of device, and you can only do that once. As long as you have the correct device defined for the download and card to be programmed, it will work. If you are changing units (say a GTN 650 for a GNS 430 then you will have to make the changes to your profile to ensure you get the correct files for the device.