Getting them 'done' before they have fully matured stunts their growth, not just physically but mentally and emotionally.
That's what I learned recently Raspberry, and why I wouldn't be in such a hurry to get it done now.
The first (our sex-mad staffie) was castrated at 3 and a half, and could still "do the business" afterwards, but of course, couldn't produce any puppies, The vet told me this shouldn't be happening, but it did!
The other three males I've had have been neutered at six months. two lived to 18 and one to only 12 (he was a yorkie - I expected him to live longer).
My daughter's great dane was castrated at 14 months. We'd hoped to wait until he was two, but he was so "humpy" and so bloomin' big, we really had to have him calmed down.
I think that nowadays, most bitches are spayed so therein less to tempt a male dog, and also very few dogs are allowed to roam the streets so there is less likelihood of them getting out and laying siege to a bitch at her back gate, risking life and limb in the process.
The health benefits for neutering dogs are much less than for bitches (I've had a botch with pyometra - it was nasty).