I think aging becomes important if you are managing a deer herd or into quality deer management.A deer that is only 3 years old still has the potential for much more antler growth. A deer may be 6 and have a smaller rack. this is one you might want to remove from the gene pool. so you can see in some cases it is important to be able to age a deer on the hoof. where I hunt (in the north) it takes 4 years before they really start to put mass into their racks.