Coffees, much like any other consumed agricultural crop, will change over time. As these coffees change, coffee roasters have to tweak out their blends in an effort to maintain a consistent blend profile.  For example, the photo at the left is the current blend recipe for Counter Culture Coffee’s “Forty-Six”.
What’s interesting is that the original blend of Forty-Six (or MAG1 as it was originally listed in the Counter Culture recipe sheet) was 33.3% French Roast (which would vary, but was typically something Central or South American like Nicaragua or Peru), 33.3% Guatemala (almost always Antigua, and from the same estate, though the name has long since left my head) and 33.3% Sumatra (from various estates, but the green buyer at the time focused on “clean”-er Sumatras rather than the crazy funkballs that you often see).
The most fascinating part of this to me is the fact that this coffee is now half African, utilizing the big berry and fruit notes from the Ethiopians to make up the flavor profile of the replaced Indonesian.  I suspect that by upping the dark roast component, they can use the lighter roasted Africans to round it out.