The Half-Blood Extraction spell converts a half-orc into a full-blooded orc. Let us say that this spell is cast on a half-orc who is 20-29 years old. This age range is young adult for a half-orc but middle-aged for a full orc.
So, once the Half-Blood Extraction spell is cast, what is the effective age of the resulting orc? Does that orc suddenly become middle aged, or should his effective age be adjusted downward so as to maintain his original age category?
I was originally gonna say you get a middle aged Orc cause you're pulling out the bit that helps keep the character young.
However, having thought that through a little more I kinda feel like you should adjust the effective age of the character to the last year of young adult.
I can't quite put it into text effectively but I figure it would keep you in the same physical state as when the spell would be cast (a young adult biology) but its also removing the part that preserved that physical state so you would immediately start... degrading (for lack of a better term). So the next time the character gets cut or sick or whatever, it heals like a middle aged orc since the biology was changed. That slow degradation to the new normal gets represented mechanically by the characters next birthday ticking them over to middle aged.
Lifespan and age categories are not racial traits. The spell doesn't effect them.
Interestingly, it doesn't seem to change appearance at all either.