I always buy my fuel in gallon jugs as well... the best thing to do is to always keep your fuel in a cool dark dry environment. Buy 1 or 2 quart bottles of fuel and keep them once they are empty. When you are going out for the day, fill the quart bottles from the gallon jugs and take one or two with you. Leave the gallon jug at home unless you think your going to burn through the whole gallon that day. Always dump your fuel from your tank if you think your not going to run them again in the next 2-3 days. NEVER put fuel from your tank BACK into your fuel jugs. Always keep a lid on your re-fuel bottle, quart bottle and gallon jug when not in the process of refueling.
Most Nitro Fuel will keep for a few YEARS if stored properly.