Opinions can change and should change as more recent research comes in.
In this case the question of "when or IF EVER to spay/neuter your dogs".
There is a preponderance of evidence that suggests "early" neutering as defined by neutering prior to boney growth plate closure does not provide health benefits; in fact it provides for many health risks and conditions that could be avoided and or minimized if one only waited until the growth plates close.
Here is one link that talks about this subject and also provides the research references.
Canine Sports Productions: Early Spay-Neuter Considerations for the Canine Athlete I believe that the dog owners should seriously weigh the health benefits versus risks to early neutering or neutering at all; AGAINST their commitment to insure no unwanted breeding occurs. Behavioural considerations of neutered versus un-neutered males? Research seems to indicate NO aggression reduction in neutering. In fact the opposite appears to happen. Marking inside is a behaviour that with time and dedication to train out of the male is definitely possible. I believe that for most dog owners neutering or spaying after growth plate closure would represent a good compromise, between health benefits and providing for you an ease of life with your pet. That is to say you don't need to worry about inadvertent breeding as your pet will be neutered after 12 or so months old.