They will eventually shut off on their own, takes about 10-minutes or so.
All of the electronics in the modern cars, and the fact the GT doesn't run the alternator all of the time means, for some users, it's a really good idea to put a maintenance charger on it if it isn't going to be used frequently. While the AGM battery is big, and can handle deeper discharge than a typical car battery, it still can give you issues if it can't get a full charge while you're out. There's a few threads on this, and you might want to read them.
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