I have to leave for 2 to 3 months at a time and leave my S plugged in and charged to 60% using my HPWC.... I use the app to check and have not seen any problems. It looses a few percent of charge, then begins to re-charge, and the process continues automatically.
The tires are slightly out of round for not having been ridden on, but that cures itself after a couple of miles of use when I return.
When the app notifies me of a software update, I have a friend who has a key to my house who initiates the update for me and the app let's me know that it updated. I can unlock the car for him from the app.
The biggest problem I have is missing the thrill of driving my S....