My snowthrower is stored in the off season April thru Oct. The manual for the engine says run the engine 'til dry, remove the spark plug and shoot in some WD40.That is what I do. But the manual for the thrower itself says fill up the tank and add a stabilizer since air and moisture in an empty tank can cause corrosion and other issues. Which is better?
If you have the possibility of shutting the fuel off (or installing a shut off valve), then both are actually right. First, always use fuel stabilizer (such as Sta-Bil) in your small equipment gasoline. This ensures you will never have to worry about it. Try to keep no more gas on hand than you'll need for a season, but since you have a snow thrower, this may be a moot point. Second, when you get done using the equipment, whether you believe you are going to use it again or not anytime soon, shut off the cut off valve and run the carburetor dry. Thirdly, fill up the tank with treated gas so it is full. If the fuel tank is plastic (as most newer equipment is these days), this is not as much of a worry. The fuel stabilizer actually keeps the fuel from absorbing any real amount of water.
I also have a small backup power generator which has to be ready to go in all seasons.Thunderstorms in summer, snowstorms in winter equals risk of power outage. My practice with the generator is to never drain the gas but run the engine about 2-3 times annually. Is that a good practice?
Keeping up maintenance on any small equipment is a good practice. There are two things I would change in your routine. First, if there isn't a cut off valve, install one. These can be purchased online or from just about any small equipment shop for a small amount of money. All you have to do is cut the hose going from the tank to the carb and throw the valve in between using the small clamps that usually come with the valve. After you run the gennie, shut off the valve and run the carb dry. Secondly, when running the gennie during its normal maintenance, attach something so it is running under load. I usually attach my shop vac to it as it draws on the order of 12 amps. It doesn't completely utilize everything my generator can produce, but puts enough load on it to give it a workout. You should, however, try to run all of the tank out every season. Fuel, even fuel containing stabilizer is only good for two years max, so running it out every year is a good thing.