Yes, a good fuel stabiliser will keep your fuel fresh during periods when you are not using your generator and in your case this should be fine.
Other good practice recommendations are:
Drain the excess fuel in the carburettor after use. All Yamaha generators have a fuel shut off valve (petcock) that you can switch off while the generator is running to use the residual fuel and ensure it does not sit in the carburettor
Start up your generator every few months for a short period to lubricate internal parts of the unit and even apply a small load to the generator ensure everything is in working order for when you need it next.