I am not aware of any flavor change clove to minty-anise as a basil matures. But the generic sweet and even to some degree the Genovese will have some variation in flavor depending on how strict the seed production (pollination)with any other basil varieties being grown in the same area. Basil cross-pollinates very easily and hence flavors can become mix in the next generation of seed. If you can find a named variety that you like (your preferred flavor) than keep getting your seed from that source. Bagging your own seed from these plants will allow you to control the flavor at your location.
I would venture to guess (I can't state it as fact) that if you bought "sweet basil" from 5 seed sources and grew them out you would find some distinct flavor differences between them. Doing cuttings from a preferred basil for it flavor is another method you can employ as they are fairly easily rooted.
Hope this helps to some degree and Happy Growing David
P.S. basil is one of my must have herbs and "Valentino" is one of my favorite Genovese strains. But flavors are personal and we have our own preferences.