I, too, have left my car for over a week in Savannah with no problems. Though in an industrial part of town, it's much nicer than other industrial-zone train stations. The station is only closed during the middle of the day and staffed through the night, so it's pretty cool.
I heard from a ticket agent at the station that a guy left a car there for nearly a year... They finally got a bit concerned and had it removed by police. Turned out the guy up and joined the merchant marines.... [Lots of the story didn't make a whole lot of sense, but it makes for nice urban legend!]