The 43-year-old is estimated to have thrown some 372,650 punches in his feat, which dwarfs the 38 hours set by Englishman Tom Varley in Cape Town.
Devenney started his marathon session at 10am on Thursday morning and at 10.42am on Saturday he thrilled the capacity crowd at the Twin Towns ABC, where he is a coach, as he summonsed all his remaining energy for a power-packed final three-minutes.
“It feels absolutely fantastic, I’m absolutely ecstatic,” he said.
“I have been in the zone for so long, dealing with pains and trying to get the thing done.
“It’s been a long journey and a very interesting journey. I’m very glad to be at the end of it.”
Ten years ago, Devenney set a new record when he punched a bag for 24 hours. Last June, he began training to attempt to surpass the 36 hours and 3 minutes set by American Ron Sarchian, but Varley since clocked 38 hours.
Allowed a five-minute break every hour, he banked up his time and took longer breaks after several hours at a time laying into the 100lb bag.
He said: “The start was very tough because I was trying not to think about the long road ahead, but I couldn’t help thinking about it.
“In the first five hours I ran into problems with the bandages on my hands and I got a cut on the left hand. That annoyed me because I thought I was going to have serious problems after that.”
On Friday at the mid-way point of his marathon session on the canvas, he was in big trouble, but revealed the inspiration to continue.
He said: “My head went down and the pain in my hands and knees got very bad. I was only half-way through. I happened to look up at a sign above the ring from my three sons – Niall, Cahir and Sean – and that drove me on.”
For the duration of his 45 hours, partner Terry, other family members and his loyal corner men Barry Gillespie, Stephen O’Reilly, Gary McCullagh, Shane McHugh, Brian Anderson and Eamon McAuley were on hand with the supplies.
Devenney said: “I couldn’t have failed with them behind me. They knew when I was down and helped pick me up.”