My Osborn Prolific (3 years old, potted but soon to go in ground) had its first good year this August. It had a lot of fruit for its size, of good quality, but they all ripened within a 3 week period, and then it was done. Is this normal for that fig ? Or is this dependent on growing conditions or maybe my imagination?  I'm not unhappy with the fruit, but I don't think I would want  too many other trees that had the bulk of their  production over a short time period. If this is normal for this tree are there others with similar time tables?

Yes and no. Figs, generally have a short season, say 4-8 weeks. Most get ripe in August and or September. Some varieties ripen over a longer period of time, and some shorter. Weather is a big factor, as well: The entire season at USDA / UC Davis this year was confined to August (with a couple exceptions, for really late season figs) because it was exceptionally warm there. Sept 1st is usually about mid season, and this year was nearly the end of the season. When I get time (yeah, right), I am going to reconstruct the ripening sequence for my trees for this season. Planting different varieties will help extend your total season, assuming your weather "season" is long enough, unlike, say, the PNW.