I'm very happy to hear that!
Future software updates of your garmin device will not affect its ability to show JCV, I've already had 1 upgrade, JCV remains.
This JCV file you have at the moment is matched with the map. Once a new map comes out, you will have to change both: map (.img file) and jcv.
About regular map updates (through myDashboard)... hmmm I don't know. If I were you, I would just keep existing files. Prior to map update, make note about size, name and properties of old files (img and jcv), run an update and then compare. I'd be happy to hear your experiences