I'm kind of under the impression that you are determined to add something to your fuel regardless. I have used stabilizers for years and dont fret about small deposits as they are a natural byproduct of raw fuel. To worry about the small downtime of the boat would be like constantly being worried about buildup in your vehicle. Carb rebuilds are a common maintenance upkeep and is just part of the boat ownership lifestyle. Again, I would not worry about it and would not be concerned about the small amount of buildup you noticed after years of service. As Achris mentioned, fuel life does well all on it's own for short time spans with no help from us.