My young male dog is going to be neutered.
I have heard a lot of mixed opinions on the best age for this, due to growth plates, hormones and so forth. As behaviour goes, he is perfect btw - no humping, never lifts his leg in the house, zero aggression and never leaves my side when out.
I seriously cannot ask for better (preens), but he is a cross, with no papers and I am not wanting to breed from him. So rather than risk another accidental litter I am having him neutered 
He is now 17 months old. His parents were both working farm dogs. Mum was Australian Kelpie and worked cattle, dad was Smooth Coated Collie and worked sheep. My dog acts as my seizure alert dog and has a co-dependent ritual with the cats whenever they enter the house: they refuse to come in unless he escorts them 
I was thinking neuter at 18 months. Is this ok? I got concerned after hearing how Smooth Coated Collies are descended from Border Collies crossed with Russian Wolfhounds. My dog carries a lot of the Russian Wolfhound traits; tall, lanky, almost mute except if alerting to an actual intruder, and nervous of his personal space when at rest. (As in he will only relax and sleep when he is with people he knows, not that he is trying to devour houseguests! He will growl if the cats walk over him when he is sleeping, but I don't blame him as they do tend to aim for the kidnies!)
So I am now wondering if it is ok to neuter him at 18 months or should he be allowed to develop for longer? And if so, how long?
Sorry for the essay and thank you in advance 