I got Cooper when he was 4 months old, per the breeders practice. He was already marking, since he had been around adult intact males. I had him neutered around 7 months and we still have issues of him marking at 5 years old
I think it all depends on the particular dog. We didn't neuter Baron until he was almost a year old (because of his size) and he never marks. He even pees squatting most of the time. I do think this is something that depends on the dog, and I'm sure training can influence the behavior though.