Don't you need to be online to start the game up though? Bit annoying.
For the first install, and first game start-up (But same if you use the disk), and then just put Steam in offline mode and continue (When the Steam updates come through you mya have to reconnect and load their updates and then go back offline again)
I leave it online, and take my laptop away from home, but just make sure you open FM13 before you leave home or put it in offline before you leave an internet connection.