A year is pushing it, and small quantities don't stabilize as well as large quantities. Sta-bil is an antibacterial that keeps sludge bacteria from growing in water condensation mixed with the fuel. That bacteria is one of the primary sources of injector and carburetor gum, but it is not the only source.
Gasoline stored in an open container, like a gas tank, also loses its lighter fractions to evaporation. The lighter fractions are what evaporate and ignite easily when the engine is cold. This can result in hard starting, even when the gasoline is otherwise OK.
By far the best way to store fuel is to rotate it often. I make up a small engine mix in 5 gallon quantities. I add 2 oz. of non-alcohol carb cleaner, 2 oz. of Marvel Mystery Oil, and the recommended quantity of Sta-Bil to every 5 gallon can, then fill it with gasoline. When the mix is about 6 months old, I pour it into a vehicle and go buy new gas.
Two cycle mix is made from the 4-cycle mix, with the addition of 2.5 oz. Red Line synthetic 2-cycle oil per gallon.
Every small engine fuel tank gets run dry at the end of its season, and the 4-cycle engines get their oil changed with Castrol Syntec 5w-50. My humble Briggs and Stratton engines run reliably for decades when treated well. Even my el-cheapo $69 2-cycle leaf blower with the plastic intake manifold starts immediately when it is needed. I have a lot of small engines. Pressure washer, riding mower, push mower, 5000 watt generator, 1200 watt generator, weed whacker, rototiller, chainsaw, leaf blower and brush chipper. They are all 100% reliable.
One comment on generators. Since my large generator sometimes goes years in between use, I not only run the tank dry, I drain the last few dribbles out of the carburetor bowl, change the oil, pull the spark plug and fog the cylinder with light oil, replace the spark plug and bag the exhaust with a plastic baggie and rubber band to keep the bugs out. Then I put it back in its cardboard shipping box, which keeps the dust off. I bought it new in 1988, and it has run through three extended power outages. That's an average of once every 5 years, so extra care in putting it away really pays off. It has a Briggs and Stratton engine.