Rooster Comb Shrinking?

My Buff Orphington Roo (love of my life!!!), is now 6 years old. He has had several offspring with our 15 hens. We live in Ohio, really cold, however, we heat our coop to about 45 degrees at all times and they do not go out below 40 degrees or when there is any snow on the ground.

He has always been very healthy, very friendly, wonderful roo and still is. I see no real behavior changes in him at all, he just finished molting about 3 months back I'd say. I've noticed that his big red comb is shrinking in size. There are no marks, spots, injuries, it is just getting smaller and it is not bold red like it was in the summer. One of his offspring is a roo, and we kept him (so far) because they do not fight at all and actually sleep by each other. His offspring roo just started crowing and mounting, and his dad my Buff Roo, was actually kind of showing him how to do it.

Could my Buff Roo shrinking comb just be aging and this is a natural part of aging with lower levels of testerone? I do not see any signs of sickness from him, just his comb getting smaller.

Any thoughts??

 

What's life expectancy for a Buff Orph roo? Do you know?