Gordon McDonald, Bill Houston and Bruce Callister have given whole blood, platelets or plasma several times a year since the 1960s.
Their donations may have helped more than 1200 people with a variety of conditions, NZ Blood (Dunedin) donor recruiter Karen Taylor said.
Mr McDonald first gave blood in the 1960s while living in Roxburgh to help out in an isolated rural community.
"I talk to the nurses to keep myself occupied, and it has got easier over time," he said.
Mr Callister was working at Cadbury Confectionery in the 1960s when he was told employees were required to give blood.
The service only came twice a year, so he joined the blood donors' register so he could make donations more regularly.
Mr Houston had "very little say about becoming a donor".
"I was an electrical apprentice and the tradesman I worked with gave blood. In those days we had to follow them around like a little dog. So off I went to give blood."
The three agreed making regular blood donations, or occasionally being on-call to give blood for medical emergencies, had become part of their lives.
Mr Callister described it as the "easiest kind of voluntary work".
"It suits me because I just lie down for an hour or so."
Ms Taylor said the centre was short by about 160 donations this year.
Each week, the Dunedin centre needed 189 whole blood, 45 plasma and six platelet donations.
About 80 signatures were gained from a recruitment drive last week.
"In Otago, we need about 1600 new donors each year, to replace those who have moved on. The theme of Blood Awareness Week reflects what we are trying to do, which is to encourage people to make regular donations," she said.
World Blood Donor Day was on Saturday.
