"Your collection was enormous," Judge Rowe said.
"The multiple ways in which you stored information demonstrates that this was a collection amassed over time."
Rowe said the thousands of images varied in their levels of abuse, but strayed into the extreme end involving rape, restraints and bestiality, which he factored into his sentencing.
"The images you possessed involved children as young as babies, right through to adolescents of about 14 years of age.
"This is not a victimless crime, these are real children who have been subjected to real abuse."
The court heard how Pickering had also recorded a pornographic live stream, which he then shared with other people on the internet.
Rowe said this was a key factor in his sentencing as it perpetuated the cycle of abuse that the children in this kind of imagery are subject to.
"You were prepared to continue the abuse by distributing it.
"They suffered not just by being abused but by having the material circulated indefinitely."
Rowe outlined how Pickering had been sexually abused as a child and suffered from PTSD from his time in the army, which he took into account when sentencing him.
He also noted that Pickering had cooperated with the Department of Internal Affairs when they raided his home, assisting them in finding one of his hard-drives they might not otherwise have found.
"Your lawyer also says that you are genuinely remorseful, and described it as an addiction and that you are thankful that the DIA came to your home and seized your computers," Rowe said.
"You feel extreme shame for what you did."
Since his arrest in 2019, Pickering had engaged with counselling service Manline to address his issues and get help.
The images and his devices were ordered to be destroyed.