I never tire watching my dogs play with one another. It's so fierce at times, but any dog owner can recognize the growls of play versus when it is a real fight. I love the "fairness" of it - not to ascribe anthromorphic characteristics to my animals, but it seems they "take turns" pinning each other in these death matches. At one time, Samson, our puppy (fyi, that's a 13-week-old blue Weimaraner) had Josie, the tri-colr Pembroke Welsh Corgi, by the throat . . . and 30 seconds later she had him in the same position.
Sam is probably about 35 pounds now, maybe even 40. He's gonna be a big boy.