I've found it to be more of a factor of how many times you open the container. Constant opening and closing and put fuel from your fuel bottle back in the container etc. etc. will shorten the lifespan much faster. I usually throw out the last inch of a gallon because it is starting to cause erratic tuning. Problems idling and transitioning seem to sprout up at the end which is as little as a month with constant opening and closing. New fuel cures it so I just don't mess around.