The earliest possible release date for the teenage boy - known as Boy A - who murdered and sexually assaulted schoolgirl Ana Kriégel is June 2031, the Central Criminal Court has heard.
The earliest release date for Boy B, who lured the "lonely and vulnerable" 14-year-old to the abandoned farmhouse and watched as she was violently sexually assaulted, is June 2027.
Mr Justice Paul McDermott also ordered that probation, governor and education reports be prepared every two years for the benefit of the reviewing court, once the boys are released from Oberstown detention centre and placed in custody.
The boys, now aged 15, will be detained at the young offenders detention centre until they turn 18 when they will be moved to an adult prison.
The judge said the reports were not intended to "micro-manage" the boys' sentences, but to give the court a clear view of what has happened in the course of their detention.
Last Tuesday, Boy A was sentenced to life with a review after 12 years. He also received eight years for aggravated sexual assault.
Boy B was sentenced to 15 years detention with a review after eight years. Both boys' sentences were backdated to when they were convicted last June.
Sentencing the boys, the judge ordered that reports be furnished to the court ahead of their reviews so that their development from teenagers into men could be assessed by the court.
Following that review a judge may impose a fixed date term.
The case was back before Mr Justice McDermott today to consider additional reports concerning the boys, once they leave the detention centre and the review date for Boy B.
The judge said the appropriate date for Boy B's review should be 19 January 2026 and not 13 January 2025 as mentioned at the sentence hearing.
A review of Boy A's sentence will take place in January 2029.
At today's brief hearing, Mr Justice McDermott said he wanted the court to be kept fully informed about the boys' progress and development in custody.
"This is not intended for the purposes of micro-managing the sentencing and is not to be viewed as such," he said.
The judge said that the boys' first period in detention would bring them to when they are 18, when they will be transferred to an adult facility at age 18 years and six months.
Reports on their engagement with educational, psychological and psychiatric services would be of assistance to those taking over their custody, he said.
There should also be a plan for their further development while in prison.
Reports should then be prepared at two year intervals, chronicling what has happened, which would be available to the courts at the time of their review.
After the boys' transfer to adult prisons in 2022, reports should be submitted in 2024, 2026 and 2028, he said.
"They are not reports for the purpose of micro-managing the sentences, it is for the courts to have a very clear view of what's happened during the course of their detention," he repeated.
The judge said there had been a request from Oberstown that the boys' psychiatric and psychological reports be made available to them to assist in the course of their work over the next couple of years.
"I don't wish it to trespass on any work they are doing," he said, adding that he does not have a difficulty unless others have.
Senior Counsel Brendan Grehan for the Director of Public Prosecutions (DPP) said the request was purely a matter for the court and the two boys. A legal representative for Boy B said he would have to take instructions from his client.
Mr Grehan said in Boy A's case, his sentence would be reviewed effectively on the 12th anniversary of the date of conviction. The review process would begin in January 2029 and the earliest he could expect to be released from "the custodial portion" was 18 June 2031, he said.
The barrister said Boy B has a minimum of eight years to serve so the earliest date he can be expected to be released is 18 June 2027.
In reply, Mr Justice McDermott said this was the intention of the court.
At last Tuesday's sentence hearing, the judge said that how both boys faced up to their culpability while in custody would be a factor in determining how long they would eventually end up being detained.
The two boys were 13 years old when they murdered Ana Kriégel in an abandoned house at Laraghcon, Clonee Road, Lucan on 14 May 2018.
They were convicted by unanimous jury verdicts last June.
Boy A was also convicted of Ana's aggravated sexual assault in a manner that involved serious violence to her.