Two notes about storage, and a warning -
1. Gasoline can most certainly be stored for longer than 3-4 months before having the problems you describe. At least if it was Amoco's best (gold, if I recall their naming correctly), from the mid 1990s - don't know about today, of course. My bike was left in the U.S., and when visiting, I would use the left over gas - cranked with no problem even after a year (however, I did drain the carbs before leaving - and when I originally bought the bike, the fuel had gummed, since it hadn't been ridden for a while).
2. The dealer I know was also unconcerned about storage times for gasoline or diesel, and was somewhat skeptical about my past experiences. Of course, he was also unfamilar with the idea of storing gasoline or diesel for any amount of time. (although heating oil may be stored for months in a home tank between two winters).

The warning is simple - don't store gasoline anywhere where people live, or in a structure which you care about, or with anything valuable. Gasoline is very dangerous, a fact which seems almost impossible to get across to most people. I am certain that in a shortage situation, a number of people will suffer horribly when they attempt to hoard gasoline.