I only use ethanol-free fuel, stored in leak-tight steel containers (the old-school Jerry cans, with good gaskets, with the lids screwed on tight). I have E-0 gasoline from two years ago (I label the fill date on blue painter's tape on each container) that I am now opening and using, and it still works just fine. For some containers that I know I won't open for a long time, I use Pri-G stabilizer, available online. I leave my equipment gas tanks filled up all winter and everything starts right up in the spring. I was just at the MIL's place doing the fall yard cleanup last Saturday. The mower and trimmer haven't been started since July. Both fired right up on the first pull, on the gas that they had sitting in their tanks.
Ethanol-free gasoline has been a game-changer for me with all of the outdoor power equipment. It saves me tens of hours per year in not messing with gunked-up carburetors and brittle fuel lines. Of course, I'm old enough to have grown up and been mowing lawns as a kid before they thought of adding alcohol to the gas.
A bit of seafoam will help the carburetor to stay clean, but isn't necessary if you are already using E-0 fuel and have a clean carb to start with. The Marvel oil may help upper cylinder lubrication, but also may contribute to excessive deposits on your spark plug. If you are happy with your results, go with what you do now.