Yesterday marked his 350th time donating at the New Zealand Blood Service’s Dunedin Donor Centre, an occasion celebrated by staff with balloons and sweet treats.
The 56-year-old was one of the top five donors ever in Otago, and at present had the highest number of donations.
Mr Armishaw said he started donating blood in 1980 at 16 years old, following in the footsteps of his father.
Ever since, he had given blood regularly, and in 2013 began donating plasma every two weeks "like clockwork".
"I don’t know how much I’ve given but it would definitely be a lot."
The process of donating plasma took 60 to 90 minutes, and was "a worthwhile cause".
"I like coming in and knowing I am helping someone every time. It’s become a part of my life."
Appreciative of Mr Armishaw’s efforts was donor technician Vicki Richardson, who knew first hand the importance of donating.
Ms Richardson’s daughter suffered from Kawasaki disease as a baby, a condition primarily affecting children under 5, causing inflammation in the blood vessels.
She received plasma product as a baby and survived as a result.
Ms Richardson said it was "a simple but significant thing for people to do".
"I think some of the best people are those who choose to donate blood."
Her daughter Ariana Paul (20) had recently started making donations herself.
"It’s nice to know something that saved my life, I can now give to help others."
World Blood Donor Day is next Sunday.