The following italics is from an Edelbrock document. 10% ethanoll blended gasoline will tend to clean the fuel system, so if it dirty, at the very least, you might need to change your fuel filter more frequently. Keeping the gas tank full won't hurt, but since the system is vented, not sure how much good it will do.
Typically, two types of blended fuels are available: Gasohol and gasahol. Gasohol is a blend of not more than 10% ethanol and gasoline. As long as there is no more than 10% ethanol mixed with the gasoline you carburetor will function properly. As the percentage of ethanol climbs above10%, a richer A/F ratio will be required. Also, because gasohol is more volatile than gasoline, hard hot starting and poor hot weather driveability may result.
Gasahol can be a blend of either ethanol, methanol or other alcohol with gasoline. Methanol blended fuel should not be used as it will cause corrosion of the fuel system components. It can also cause rapid failure of seals, gaskets, diaphragms and pump plungers.
Always check to see if you are using a blended fuel. Although the pump may not indicate the fuel is blended, it is always advisable to verify the type of fuel the station carries.
As a side note to the statement above about richer with more than a 10% blend of ethanol. Typical air / fuel ratio for gasoline is 14 - 15:1, for pure ethanol it is more like 9:1.