Short answer is if it does anything, its not much. This is after 19 months, now, they started it every month. I believe there is an even later one where only the VP non ethanol fuel works.
You're storing your car over the winter, don't worry about it.
As for your lawn equipment, at least make sure the carburator is dry by closing the fuel shut off if it has one and then run it until it dies. Otherwise, drain it and store it dry.
On most a-bodies, the gas is exposed to air all the time, so I would generally say have the least amount left in there for spring as you can and go fill it up right away. If your environment is super damp, not really sure what to say other than its not the best.
