The one problem I had was when I forgot to drain the carb on my Honda 2 HP 4 stroke outboard. The float bowl was full of nasty debris. I have a Honda generator that I replace the fuel once a year. It starts right up on the year old fuel. Did have a small problem with debris or a stuck float but not sure it was because of old fuel, maybe stuff in the tank, it is over 20 years old. I do, however, drain the carbs on my outboards, snow blower and generator. Running them dry leaves a small bit of fuel in the bowl.
I have also used this for many years:
B-12 Chemtool® Carburetor, Fuel System and Injector Cleaner | Berryman Products
FWIW, I bought a new Tohatsu 6HP 4 stroke about 2 years ago. Use it a lot, ran/runs perfectly right out of the box at 6,000 feet elevation, no tweaks or adjustments necessary.