Buy a Honda lawnmower and you won't have a problem. Ours sits from late Sept until probably the first of June this year. I still have eight inches of snow in the back yard. That's going to be seven months of sitting with nothing but standard fuel in the tank and I expect it to start on the third pull.
My Arctic Cat snowmachines sit all summer with no additives and they start every February on the third pull.
One of my chain saws with the long bar only gets started every other year and it always starts on the third or forth pull with no additives.
I did buy a jug of Stabil, but never seem to remember to use it since everything seems to work without it.
It doesn't hurt to drain the fuel bowl on the generator, but if it's going to sit for less than a year, and everything is tight, the fuel shouldn't evaporate to leave any gummy residue to cause problems. Stabil won't hurt anything easier, but so far I haven't found a need for it.
Bill