I'll add my experience here.
My Mustang sits in the garage from ~November to May. No additives added and no issues for the last 10 years(when it was carburated or now that it is fuel injected). Storage method is simply turn the key off.
My other "toy" a VW powered dune buggy it is only used 1 week in August and 1 or 2 days around Christmas. Stored outside, no additives, just turn the key off and walk away. I have cleaned the carb twice since 1989.
My parents have a '48 Willy's jeep. It sits in storage from September to June, gas tank topped off and battery disconnected (stored like this since 1948) and no problems. The first time the carb was taken apart and cleaned was the summer of 2010.
