"Man, that's a long time to be in any field today," Mr Austin said, presenting Ms Edwards with a voucher for a weekend away in Taupo.
"She's a really calming influence at this place ... done a stunning job," he said.
Mr Austin also had awards and certificates for Suzi Aki, for 16 years' service, and Joy Ngatuere, 17 years. He said it was "pretty special to be able to do what we've done today".
The awards were celebrated with a special afternoon tea.