I spent 3 days at a Deer Farming Seminar this March. This is one of the topics that was discussed heavily. The quality of offspring the deer will produce declines after about 6.5 years of age. As soon as the antlers start going down hill so does his offspring quality. Reality is though this conversation is a mute point in most places. The deer don't live long enough to ever degrade and with out truely controling what deer is breeding with which other deer the young deer will typically breed more deer than that older deer anyway. While the older deer is busy defending his doe the young ones are just running around servicing anything they can.