A fasting blood sugar of 80-120 is considered normal whether you're 21 or 60.
"I'm quite sure that same body conditon if applied to a 21 year old would not be so great."
You're comparing apples and oranges
Regarding the "young vs older person" scenario, it would appear to me that a pancreas that has been pumping insulin for 60 years would not be as efficient or in as great a shape as a pancreas which has been pumping insulin for only 21 years. Time will take it's toll on everything. We've all heard medical personnel say "for a 60 or 70 year old that person is in great shape". I'm quite sure that same body conditon if applied to a 21 year old would not be so great.
Glucose rise with age? No. I don't know of anyone who consistently hits the same fasting number every single time. Fasting levels between 70 (some say 72) and 100 are considered good. Keep in mind the optimum number is in the middle. The closer you are to 70 or 100 you run the risk. Nutrition and exercise are the keys to a healthy non-diabetic body.