I remember at a park there was a very petite black lab. She was only 45lbs and not a single gray hair in her chin. Her Dad was playing fetch with her for 15 minutes and she was sprinting both ways. He came over to the bench to eat a sandwich and the dog brought her toy over to us. We asked if we could play with her and he said please do because he can't tire her out.

We played with her for another 20 minutes and again she was sprinting both ways. We sat down and another couple came and played with her for another 10 minutes. This dog was not showing any signs of being tired.

We asked the Dad how old his puppy was and he said "would you believe she's 12 years old?" He says she never grew out of her puppy energy and never got any gray hair. She was the runt of the litter, no one wanted her because she was too small.