You only need to run it to assure you that it is working.

Generac suggests you maintain it every season (4 times a year).

Generac has definite information in their manual about storing the generator for extended periods (both gasoline and corrosion protection, especially important if you're in certain humid environs).

On shutdown, the carburetor should be drained of fuel. One way is to shut off the fuel line and allow the engine to run until it quits. The other option, if present, is to shut off the fuel and drain the carburetor after the engine is shut off. This latter option is the better one.

The object is to empty the carburetor for storage. The second option above is the better one because very likely the engine will quit running before the carburetor is completely empty. The reason for doing this is that the fuel will evaporate leaving behind deposits that can clog small passages. If permitted by the engine maker, its a good idea to protect the fuel stored in the tank with an additive to slow oxidation and deterioration of the fuel. Use what the manufacturer recommends. For my engines, I have had good results with a product called "Stabil". Its available at automotive supply stores.

Since all my small engines are compatible with Stabil, I use it in the gas can storing my gasoline supply. This procedure has greatly reduced fuel problems for my lawn mowers, trimmer, and chain saws.

The owner's manual for your generator should have recommendations for shut down and storage.

I converted my 7500 W Portable generator to run on propane. I use the generator solely to provide power to my home during local power outages.

Some advantages are: propane is safr to store than gasoline, it also burns cleaner. Propane does not go "bad" with time and propane does not gum up the carburetor if the machine stands idle for an extended period.

Most importantly, during an lengthy area wide power outage gasoline can become difficult to obtain. Many stations in this area have no electrical backup available to run their pumps, and the few that do have power are swamped with motorists AND fellow generator owners.

I ran in my generator on gasoline and have used propane only since that day.

I still have to run my portable propane fueled generator periodically to heat it up and illiminate any moisture condensate.

And you do need to change the oil periodically, even with propane.