Two of the charges represented multiple offending, and there were 10 acts, with Brown paying the boy $200 a time, apart from the last when he gifted a cellphone.
In his trial he had defended the charges on the basis of his belief that he was in a relationship with the consenting male and entitled to believe he was aged over 16.
In court today, as the victim sat in the public gallery, Brown accepted he had "made a mistake", and that he should have taken steps to ascertain the victim's correct age, but Crown prosecutor Clayton Walker and the Judge both said the attitude highlighted Brown's penchant for blaming his young victims and his lack of insight into the harm he was causing.
Brown had previously been sentenced to nine months' supervision in 1995 for indecently assaulting a 14-year-old boy, to nine years' jail with a minimum non-parole term of six years in 2006 on nine charges relating to offences with three boys aged 13-15 years, and a further six months for offences on two more boys in 2005-2006, and on his only recorded adult victim, a fellow inmate in prison.
Justice Doogue noted that judges in 2006 and 2008, had decided against sentences of preventive detention, firstly by a "fine margin" and secondly only because Brown hadn't at the time started treatment programmes in prison.
The latest offending showed Brown had not responded to the eventual treatment, and she did not accept defence counsel Richard Stone's submission opposing the application for preventive detention which was made by Crown prosecutor Clayton Walker.
It included not accepting the submission that Brown's advancing age, turning "60 next year," made him any lesser a risk of reoffending.
Stone said there was no "grooming" of the boy, who he said had used the Grindr app to seek partners and had "portrayed" himself as an 18-year-old EIT student.
Victims in previous offending had mainly been boys Brown got to work with him while he was involved in rural contracting.
Walker said the payments in the latest events were a form of grooming, in a situation with a 44-year age gap and an offender still targeting pre-pubescent boys, claiming it was still a proper relationship, with a reluctance to accept a court's finding.
One report had noted a "psychopathic" trait in the offender, but he was not deemed to be suffering mental or physical illness such that it would be a factor in the sentence.
Justice Doogue said the physical nature of the latest offences showed an "escalation" of the activity rather than a situation of less risk.
In 2008, two prison officers and two security officers wrestled a struggling and kicking Brown to the floor of the same courtroom after he reacted angrily to guilty verdicts at the end of a trial in which he had conducted his own defence and, not for the first time, claimed accusers were lying.