He came close once, managing to slip into place while the minister was delivering his piece just before Mr Cowles was due to perform the Last Post and reveille.
But this year could be his last - Mr Cowles hopes to hand the duty to a younger player in the Oamaru Garrison Band.
He has a teenager in mind, but whether he can fill the role depends on his plans when he leaves school.
If no-one can be found, he will fill in next year but the 71-year-old hopes that will not be the case.
"I'm getting a bit past it," he said with a smile.
Mr Cowles attended his first Anzac Day service in 1962 as a 21-year-old member of the garrison band. As trumpeter, he was chosen by the band leader to take the role.
Since then, he has played the Last Post and reveille on Anzac Day at the dawn parade at the World War 1 monument, the wreath-laying at the Oamaru Solders' Cemetery, the ceremony at the Turakina Monument at Lookout Point and the main parade and service at the Boer War, World War 1 and Garden of Memories (World War 2) monuments.
He remembers one Anzac Day when he also travelled around country services, playing the Last Post nine times and reveille 10.
Yesterday, at the completion of the main Anzac service at the Garden of Memories, band members applauded Mr Cowles' performance.
Milton bugler Graham Powell is a novice in comparison. He has been playing his trumpet at Anzac Day services for only four years.
Each Anzac Day, he starts with the dawn service in Fairfax near Milton, then at Lovells Flat, and finally the Milton service.
"I enjoy it. You're not actually thinking just of your relatives but also those who gave their lives. It's my way of saluting them."
Mr Powell moved to New Zealand five years ago, first living in Oamaru for a short time before moving to Milton.
For the past four years, Mr Powell has worked as a Corrections officer at the Otago Corrections Facility at Milburn, and has been bugling for the wider Milton area for the same period.
While he loves his role as bugler, the task is not without its struggles, particularly early in the morning.
"On a really cold day it can be quite difficult. Last year's service at Lovells Flat was by far the coldest I have had to play in.
"It was a struggle to keep the trumpet warm enough."
Mr Powell served in the British Army for 23 years, achieving the rank of warrant officer, second class.
He also served as the brigadier's bugler during that time.
