"He would have continued to offend had he not been stopped."
Laurence targeted vulnerable young boys and posted images of his offending on the internet to be viewed by other paedophiles, which could never be retrieved, Mr Murray said.
Laurence wrote a letter to the court expressing his regret and remorse, which was read by his lawyer Gary Turkington.
"I believe I would no longer be a threat to the community with support.
"I will not cause harm again," he promised.
Laurence said he failed in his responsibility to protect the young boys he was looking after.
Justice David Collins said that while he was eligible for preventive detention, there was not sufficient information to impose that sentence.
He said Laurence would befriend vulnerable boys and invite them to his house with promises of PlayStation, food and cigarettes.
Often the boys would be abused while they were asleep, which Laurence recorded and downloaded on the internet through a file sharing website.
He had more than 31,000 objectionable images and videos on his computer, Justice Collins said.
The victim impact statements made for "chilling reading", he said.
A sentence of 12 years and nine months denounced Laurence's offending and protected the public, he said.
Meanwhile, police said a joint approach to uncovering sex offenders contributed to the successful conviction and sentencing of the active paedophile.
As a result of the investigation, two children from overseas were rescued from further sex abuse in their home country.
Officer in charge of the case Detective Senior Sergeant Kylie Schaare said a joint investigation by the Wellington District Child Protection Team and the specialist police unit OCEANZ (Online Child Exploitation Across New Zealand) had proved highly successful.
"Our response to the sexual abuse of children is very comprehensive and with a joint approach between districts and OCEANZ, we have a range of resources that can be effectively used to investigate the sexual abuse of children," Ms Schaare said.
"Child sex offenders should be put on notice that our approach to this type of crime is proactive - we do not sit around and wait for complaints to be received - we are actively seeking those individuals who would offend against our most vulnerable members of society."
Ms Schaare issued a warning to child sex offenders: "`If you seek to exploit children either in the virtual or real world, rest assured that we will catch you eventually and hold you to account."
