I use it regularly (yearly) on my bike and lawnmower. I only use it though if I have a full tank of gas and will not use the equipment for a while. In other words towards the end of Fall if I have a lot of gas in my mower or bike I will put some in. Otherwise, I'll put in fresh gas the next season and it should be fine. I started doing this after I had major gasoline problems with my motorcycle one season after leaving a full tank for a long period of time.
I believe Stabil works, but you don't use it to not have a full tank of fuel go bad. You use it to keep the carb/injectors from gumming up. With that reasoning, I don't understand why you would not use it even if the tank was almost empty ?? Of course after you mix it in, you must run the engine to get the Stabil treated fuel thru the fuel system.
I can't count the times I have had to pull carbs on Seadoos, four wheelers etc. because I procrastinated and never used the Stabil.
In the case of the thread starter, I would just put in fuel as needed toward the end of your driving season and only treat it if you have an off season when the car is parked for more than two months.