I have used fuel that is over 3 years old with no problems. I think the key is storage and that red inner cap. If fuel is stored in the dark and in a cool place or without large temp changes and the jugs have that nice inner red cap and the outside caps are tight then you have your best shot at good fuel over long storage periods. Fuel is hygroscopic (likes moisture, attracts moisture) so if sealed from the moisture it shouldn't change. Of course I should point out I'm talking about new bottles - half empty bottles will have the potential for not being as good as long cause once you start to draw fuel it's replaced by air which has moisture in it.