He was 21 when he first graduated in dentistry with honours from Sydney University.
That was 76 years ago, in 1936.
His second degree was a Doctor of Dental Surgery from a Chicago university, after which he spent many years working as a dentist in regional NSW, London and Sydney.
He completed his third degree, in law, six years ago when he was only 91, and went into the Guinness Book of Records as the world's oldest graduate.
Allan Stewart said at that time he was going to hang up his academic robes and mortar bored.
"But then, I got bored," he said.
"I have so much time on my hands these days and I like to keep mentally active."
So he enrolled in another degree through Southern Cross University's Lismore campus - and now at the age of 97 he's achieved his fourth degree - Master of Clinical Science (Complementary Medicine).
Mr Stewart walked briskly down a long flight of steps and on to the stage at SCU's Whitebrook Theatre last Friday to receive his degree and deliver the graduate address to his fellow students.
He told them he had no idea when he graduated with his first degree that he would still be learning and studying at the age of 97.
"So I would encourage each of you to embrace lifelong learning with a passion," he said.
"Never think you are too old to either begin study, or to put another qualification under your belt."
The nonagenarian practises five types of fitness: fitness of mind, body, purpose, spirit - and social fitness.
When his SCU supervisor, Dr Sonya Brownie, introduced him to the concept of "social capital" he took it on board at once.
"I invest heavily in that at every opportunity," he said.
"There is evidence that social interaction enhances the ageing body and favourably stimulates brain chemicals."
He took the complementary medicine course to enlarge his knowledge of healthy ageing.
It was not without its challenges - when he began he had little knowledge of new distance learning technologies, but quickly became proficient at using online library databases, interactive online discussion boards and Skype.
"Now I help others to master the intricacies of the worldwide web as a volunteer at the local community technology centre," he told The Echo.
Mr Stewart lives independently in his own home north of Newcastle. He has six children, one deceased, 12 grandchildren and six great-grandchildren.
He said he lives a "reasonably active life", enjoys still having an unrestricted driver's licence, and is "addicted to the computer".
He works in his garden where he grows vegetables and fruit; acts as a carer to a friend, walks, swims, cooks, and meditates.
"I'm in pretty good health, take practically no medication, and have no cardio-vascular problems," he said.
To what does he attribute the good health he's enjoying as he approaches his 100th birthday?
"To some extent it's in my genes," he replied.
"But practising the five kinds of fitness, and doing a whole body scan from the top of my head to the tips of my toes three times when I meditate probably helps."
Mr Stewart said he had no plans for further study but will share his thoughts on healthy ageing as a guest speaker at local clubs.
And although he has no plans to enter the workforce in complementary medicine, he plans to pass on his skills to family and friends if they seek his advice.
I have so much time on my hands these days and I like to keep mentally active