Judging by the antlers alone I'd say the top is 2 1/2 years old.

I don't know about the deer down south , but in the north they have a pretty good toupee on the top of their heads by 3 1/2 years old.
I don't know what you reallycall it but I always called it a toupee. That dark patch of thicker curly hair on the top of their heads.