I gave a bi-annual to a guy who was 80 one time. He was an ex-747 captian, and I worked him pretty hard to see if he would ge confused or behind the curve, but he did just great. He had this little plastic kneeboard checklist and anything that I had him do he had a checklist in there and could pull it up and do it in seconds. He was a little totering physically, but he had a valid medical, and could fly the airplane, so I signed him off.
Compliments on your professionalism. That's the way its' suppose to work.