Well I think the easy way to get a correct answer would be to ask the maker of the fuel. Here's what Morgan Fuel has to say ;

What is the shelf life of the fuel?

Unopened and stored in ideal conditions (between 60-80 degrees) it will remain usable for several (5-7) years. As the fuel begins to degrade it will increasingly lack the punch of new fuel. Really the only way to tell if the fuel is good is to run it. If it idles well and the transition is good on the ground, use it. You might notice a little less "bark" in a fuel that has been stored for several years but it won't hurt the engine.