I've had the same thing, some winters I add nothing, some years I put stabil in and haven't noticed a difference between the 2. Then again I only have a 60 gallon tank and the first few trips I baby it until I add fresh fuel anyway either way.

most modern fuel injection cars have a sealed fuel system, the tank is not vented therefore the aromatics in fuel can not escape. Most boat and carbureted systems are vented to the atmosphere and the fuel will degrade in as short a time as six months depending on the the storage conditions and vent size.

The alcohol in modern fuel is the first to go and causes bad corrosion in the process. I personally highly recommend stabil or similar and or draining the carb on anything that is going to sit more than six months.

I have lost count of the carbs I have had to remove and clean for friends

I change it every fall before I put it away and it looks pretty dirty for the amount of hours I put on it. The only reason I do that is I don't want the contaminates to form sludge and coat my engine parts.

It is changed in the spring for condensation, not oil degradation. I don't bother anymore. Mobil 1 is supposed to handle high moisture content, one good run to get it hot boils it out.

Also Stabill cleans injectors, I figure it can't hurt.