Fish, Although I'm sure your winters are colder than mine, my first winter with the GT had no electrical issues and I did not follow any special procedure. This battery episode started 18 months into the car life. I am not planning to do anything special to "prolong" the battery charge on this new battery. We will see if it was just a faulty battery or poor electronic design.
I do agree that a new battery might have solved Magnumforc's issues. Too bad the service dept. didn't pay more attention to an important customer. It is much more costly for any company to acquire a new customer than to keep an existing one.
2011 550iX GT, 2011 MB C300 sport, 2003 Porsche C2 Cab (turbo conversion)