"It seems to me there must have been an element of planning, if not preying on young and vulnerable women who you knew were in your home and on whom you carried out these acts," the judge said.
The allegations that led to the prosecution arose in 2015 when a woman came forward to say the defendant had abused her when she was a child.
Prompted by her complaint, three others came forward with similar stories.
One victim read a statement yesterday calling her ordeal "the most horrific night of my life".
"All it takes is one thought, word or feeling to provoke all the memories of that night," she said.
While some people got closure from confronting their abuser, she said it had the opposite effect: it reopened old wounds.
"I find myself with questions regularly: why didn't I fight? Why didn't I leave? Why didn't I tell my parents?"
Like her, another victim said she had self-harmed in the years following the trauma.
It was the second woman whose allegations sparked the police inquiry.
She said she was inspired by seeing a sex-abuse survivor speak on television.
Before that, her mental state reached such depths she spent time in hospital for drug addiction, the court heard.
"The offending has affected every part of my life," the victim said. "He has pretty much murdered me, because I was so young. My life was taken."
Most of the abuse took place between 1999 and 2006, the court heard.
The defendant's stepdaughter, who was targeted from the age of 3, told the jury about watching one of her friends being raped while the defendant filmed it.
The victims spoke of other instances when the man would lay them on a towel and cover them in baby oil or powder.
One spoke about a scenario where all four girls were on the defendant's bed and were forced to take turns lying next to him.
She told the jury how her abuser would play adult movies for the girls and was ''always sexual'', at which she became upset and asked to go home on one occasion.
The defendant threatened to put her in a dog kennel if she did not behave.
In a recent presentence interview, he continued to deny the offending and claimed he was "set up" by the quartet.
But after being visited in prison by his counsel, Bill Dawkins, three weeks ago he wrote apology letters making some concessions.
"Arguably there's a bit of minimising still going on, they're not articulate ... parts seem to be a bit clumsy. But the point I try to make is ... it's a start," Mr Dawkins said.
Judge Crosbie said the letters were not indicative of genuine remorse.
"They fall short of that," he said. "You apologise for emotional harm. You apologise for overstepping the mark ... a complete understatement. Where you say you apologise for your behaviour, your letters don't take ownership of what that behaviour was."
The judge imposed a minimum non-parole period of six years and two months.
