Clinton Travis Oliver, 45, and Braydon Franklin, 35, were found guilty by a jury after being charged with murdering Donna Louise Howe and interfering with her corpse.
Oliver was a housemate of Ms Howe while Franklin was a frequent visitor to her home in Caboolture, north of Brisbane.
The pair killed the grandmother, 57, on Mother's Day 2022 before rolling her body in a rug and leaving it in a vehicle for a day.
The body was then dumped and set alight near Beerburrum, in the Glass House Mountains, about an hour north of Brisbane.
The duo remained at the scene for hours as Ms Howe's body burned.
Her skeletal remains were not found until June 7, two days after Ms Howe's daughter went to police, worried her calls and texts to her mum had not been returned.
A Brisbane Supreme Court jury heard there had been tension over suspicions Ms Howe had stolen property from the two men.
In a victim impact statement, Ms Howe's mother Margaret Ellem on Wednesday said her daughter had been taken from her family in a senseless act of violence.
"That is the day my whole world fell apart," she said as family members wept in the public gallery.
"To think she had been thrown away like rubbish is beyond belief."
She said she no longer celebrated Mother's Day - the day her daughter had been killed - or New Year's Day, which was Ms Howe's birthday.
"Your horrendous act has devastated our family."
Ms Howe's daughter noted her mother had taken in Oliver and his then-partner, along with Franklin's then-partner.
"Mum had a heart of gold and would give you the shirt off her back, as she did for all those involved in her death," Tiana Howe said.
"All her kindness taken for granted, and for her life to be taken by the ones she was trying to help."
The former partners of Oliver and Franklin - Cassie Ann Reid and Chelsea Butterworth - have both previously pleaded guilty to being accessories after the fact.
In sentencing, Justice Martin Burns said the two men had shown themselves to be "devoid of any shred of human decency".
The court had earlier heard the pair had taken over Ms Howe's house following her death.
Oliver lied when her daughter asked about Ms Howe's whereabouts, saying she had gone on holidays and made copies of her financial account details.
Justice Burns described Oliver as the man most motivated to murder Ms Howe and who struck the fatal blow in an ambush attack, probably with a hammer.
"She would have had no inkling she was about to be set upon," Justice Burns said.
He called the actions of Oliver and Franklin "senseless and barbaric".
"These were, in my assessment, acts of extreme cowardice, savagely assailing a 57-year-old grandmother in her own home," Justice Burns said.
"You conducted yourselves in the most shameless of ways, without the slightest shred of remorse or regret."
He regarded the second charge - interfering with a corpse - in the worst possible category of the offence.
Both men received a life sentence for murder and the maximum five years for interference with a corpse, to be served concurrently.
The minimum 20-year parole period was increased to 21 years for the duo due to their "atrocious" post-murder conduct which compounded the grief of loved ones, Justice Burns said.
Oliver will not be eligible for parole until June 2043.
Franklin will not be eligible for release until November 2044.
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