Long season usually refers to the length of season required to ripen a particular variety. A "long season" fig usually ripens later in the season (takes a longer time too mature) which means it needs a longer warm/hot season to ripen successfully. This generally happens in location that are closer to the equator (think California or Texas) rather than northern areas (think Minnesota, Canada) The same idea applies for corn, cucumbers, etc, often referred to as "days to maturity" and arr often governed by such things things as "last frost date" and "first frost date".
A variety that ripens over a greater amount of weeks (6 weeks instead of 3) is a different issue. Genetics may dictate that the figs ripen relatively close together in time. If you watch some varieties set fruit, the first fig appears, and then anotgher in a day, or two or three, and then another. Some varieties will continue to set fruit as long as the weather is warm enough to encourage growth. The figs that form later will ripen later, and how many ripen will be determined by how long your season is, When it gets too cool they will go through the ripening "process" but will not be desirable to eat because of the lack of flavor and sugars because of the lack of sun and/or heat.