I dunno, I've left fuel in many vehicles for over 6 months and never had a problem. From boats to cars to pickups to bikes. I know the octane level diminished, but the vehicle still ran fine. I always try to ensure the tank is topped off before long storage, too. Matter of fact, my dealer said to ensure you have fuel left in the system so the seals and what-not don't dry out.

Of course your mileage may vary.