I have a yellow labrador that I got six months ago. He is almost four and a half, but has not been neutered by previous owners. Are there any problems associated with neutering at this age or should I just go ahead and do it? Have to say, his balls are rather unsightly, so I'd be glad to see them go!
With male dogs beyond population control there is no benefit in doing it in a young dog and a middle aged one. I would make sure he has had plenty of time to settle in with you before he had the op though.
I'd go for it, if you want to see if it makes any difference to his behaviour you can get him a Suprelorin implant (injected like a microchip) which lasts up to a year - I did that with my boy as I left it really late and it worked a treat!