I'm a big proponent of using the proper oil, FRESH good quality fuel and maintaining a clean fuel tank. Sta-Bil is the only thing I'd add to the fuel aside perhaps 2-stroke oil. My fuel is never more than a couple weeks old and I empty the fuel tank completely during winter so sta-bil doesn't make sense for me.
If/when it finally begins lean-hesitating and falling on it's face due to fuel system issues just fix the problem, mechanic in a can will not resolve anything.
The old factory Grey Tempo fuel lines bring on the carburetor plugging and clogging issues earlier due to they decompose and corrode internally so if you still have them on there it's a great opportunity to D&C those carbs at the same time.