Fifty-six years later they are calling time on their careers, leaving more than 100 years of combined experience behind.
Each of them started at St John as cadets and often coached or mentored each other throughout the years.
"You work probably more than you spend time with your own family," Mr Bain said.
"They've got to have your back."
The 63-year-old had been an intensive care paramedic for the order much of his career, something he wanted to do since his childhood and was encouraged to do by his mother.
"I love waking up and going to work every day."
He was "retiring early" and wanted to get out early and enjoy life, he said.
"St John is a big family and it's what you make it.
"When I first started the job I was handed the baton from those that were retired and now I'm passing it on to a great group of people."
Ms Buchanan, who is the district operations manager for Southland Lakes, grew up in Mataura and her mother, who was an ambulance officer, kept her occupied by pushing her towards being a part of St John.
She and Mr Bain often crossed paths during their work and built a beneficial relationship.
Despite her retirement, at 67 years old she would still keep "a few fingers in the fire", she said.
"Life's very short in the big picture and I've seen people die prematurely.
"We lost our own son earlier this year and I think that made me realise, retire when you've still got your health and can enjoy your retirement, because so many people leave it too long."
Mr Bain officially finished on Monday and Ms Buchanan will finish on January 17.
