I had Molly spayed as early as possible, but I waited on King until he was 3, as I have seen so many great young male pups with great personalities that after neutering were never the same, kind of dulled, I guess. King hasn't changed a bit, personality wise (This might be a negative in some people's opinions, King has a ton of personality!
), and the only physical changes we saw was he just wasn't quite as rock hard as he was before.
Of course, there was a negative to waiting, as King fathered 8 pups before he was a year old, due to the neighbor's dog running loose and jumping my fence. All those pups found good homes, so it worked out. I was going to take one of them if needed, as King and Molly both seemed to accept the pups jumping all over them when we walked over to visit pretty well.
My last dog, Gus, was never neutered, and he was put down at age 14.5. The vet said he thought it was prostate cancer from the looks of it. He said it was the worst he had ever seen and that Gus appeared to be pain free was a miracle and said if Gus was a human, he would have been screaming for morphine, or just to die.