Honestly, don't keep the gas that long. Put it in another vehicle, burn it (the premix oil won't hurt a 4-stroke engine), and buy some fresh when you get back. There is no fuel stabilizer out there that will work 100%.
Ethanol in today's fuel blends will attract water from the atmosphere, and it causes phase separation in the gasoline over time. Even if you can get the gasoline to stay "together" on a molecular level, it will get contaminated by water if left to sit that long in a container where even some air can get in.
Trust me, I deal with bad gas all the time at work. The only product out there that works and I'd recommend is Star-Tron (in a blue bottle), but even it is marketed more as a "fuel treatment" than a "fuel stabilizer".
Get rid of the gas and buy fresh when you get back. That's the only way you can be sure that the carburetor doesn't gum up or that you don't blow up your engine from detonation caused by low-octane dead gas.