If it sits more than a month or two, you'll likely come back to a dead battery if it's not started or put on a trickle/float charger. I've successfully had cars sit 3+ years before and crank right up as if they had been started 5 minutes before as long as they're kept in a controlled environment and not subjected to serious temperature fluctuations/moisture.
My S2000 has only had 400 miles put on it in the last year since I had my last state inspection done on it. Whenever I take it out, it gets fully up to normal operating temperature so all of the fuel dilution (if any) in the oil gets burned off... I change the oil about once every year or two in that car since I'm running M1. If you're not driving the vehicle, what's the difference if the oil sits in the crankcase or if it sits in a bottle on the shelf? Not really much difference, IMO.
Ricky