I learned (as a lad) about "degraded fuel, when after spending a whole day trying to get a long-stored motorcycle running, my Dad said "try some fresh petrol". Blow me, it started first time! The "old" petrol, - actually only 2 or 3 years old - had a different smell.
For a couple of decades (Since I rotted a few new replacement exhausts, etc., and spent ages polishing greyed aluminium cases) I have been winter storing bikes while the Council dump huge amounts of salt onto the roads, to add to the salt that blows from the North Sea, just a mile away. So for 4 to 6 months, starting the bike roughly monthly, I have noticed how starting gets much worse after Christmas, when the fuel is more than 3 months old. Usually by April, I am draining half a tank or more out and replacing with some fresh, then burning the old with new through the season. A chemist told me it is natural degradation in petrol and always has been!
But he advised Diesel is worse, as there is a "splash" of something that helps "instant starting" in DERV (~25% naphthalenes and alkylbenzenes?), but the very volatile light fractions can leach through plastic storage bottles, and when it is gone the DERV isn't really DERV any more, just oil-fuel. - And that makes it harder for the first ignition to happen. Whatever makes "old" fuel a poor starter is probably not a bad thing really, as I like to crank an engine until the oil warning lamp goes out before letting it fire-up, after it has been standing for a month or more. Usually I do this before turning-ON the fuel tap, or while waiting for the float bowls to fill.
I keep carbs dry-ish by running with fuel off until the engine dies, before storing.
Not experienced Ethanol problems yet, as I use the lowest available ethanol, highest octane, plus valve lube and octane booster, as it it 5 years or more since the leaded stuff dried up in N.E. England.
But not a problem for models, just long-term storage of petrol for the models! I use a very old (WW2) brass container, with lead screw top, and cork gasket. - It has not rotted - yet.