Ive never gotten the green slime, but can't really say why. I fog my motor down each race day, and always store my bowls full. If I run them dry, it'll develop a white chalky substance that wipes away with some WD40. Race gas seems to eat away and cause corrosion just as bad, based on the carbs I've pulled off the shelves that had leftover fuel in them. Also, I don't worry about my tank vent...no way enough moisture will find that opening and spoil the fuel in the tank unless perhaps you're parking is some really damp garages.
Most pumps now are alchohol/ethanol compatible, so the O rings should be fine.
