I'm sure the fuel companies do plan on their fuel to be good for a year, but simple fact is, it just doesn't happen.
As far as Sta-Bil not fighting ethanol, that's the principle reason Sta-Bil is on the market!
Features & Benefits
Marine formula STA-BIL contains double the corrosion inhibitor than original STA-BIL, which is important in open fuel systems, such as those found in boats, lawnmowers and snowmobiles. Open fuel systems vent to the air and continually attract water from the air. This became especially true since the introduction of ethanol blended gasoline that attracts water. When water is introduced into a fuel system it can cause corrosion damage to fuel tanks, fuel lines, carburetors and injectors. Marine formula STA-BIL will protect your engine against these damaging problems.
Best ethanol problem fighter
Prevents corrosion from moisture and ethanol induced water attraction
Double the corrosion protector than regular STA-BIL
More than four times the fuel system cleaner than regular STA-BIL
Kent - '03 Fleetwood Storm Ford F-53 V-10
With Susie (Lhasa); Angie (Shorkie) Ferbie (ShihTzu)
In Memoriam: Katie, Spencer and Zoey