Ethanol absorbs water anyway, do you want 3 gallons of gas with water in it or 18? I have personally done this for 20 years and my dad did the same with his 1983 Mustang 5.0 he had for an additional 10 past that. They'll run in the spring and then you have fresh gas right away because you go right to the gas station after the car warms up. I'd be more worried about the gas spoiling than the water in most places.
My garage is insulated, but not heated - in any case, a car that's driven in salt is like 5' away from it and there's never a problem.
You'll lose a measurable amount of fuel to evaporation in these over the period of time. I honestly wish someone would bust the myth of the whole thing about storing it full. I worked on enough "not working" lawn equipment stored that way to know better. The air is signifigantly drier in the winter when it's below freezing anyway.
