Councillors Sam Neill, Trevor Kempton, Doug Brown and Ella Lawton have confirmed they will not stand in October's elections.
Chairman Stephen Woodhead, deputy chairwoman Gretchen Robertson, Michael Laws, Carmen Hope, Bryan Scott and Andrew Noone have said they are either standing or likely to stand.
Councillors Graeme Bell and Michael Deaker are undecided.
Cr Brown, who is the sole Moeraki candidate, was the longest serving at 21 years.
After that tenure, it was time to step down, he said.
"I hope some younger people will come along and some people from the rural community will step up."
Things had changed a lot at the council in his time, including the workload getting "a lot bigger".
There was "plenty of work to be done" with a score of water changes.
Cr Sam Neill, from the Dunedin constituency, had been on the board for 12 years, which he thought was "long enough".
He would like to see balance on the council between new blood and people who could understand the issues.
"That institutional knowledge is still worth a lot."
Cr Lawton said she would not run as she was moving from Wanaka to Invercargill to be with her partner.
She secured the seat after winning a by-election triggered by the death of her mother, Maggie.
In her time there, the regional council's relationship with territorial authorities had improved, Cr Lawton said.
However, there was still a long-standing problem of governance not keeping the council to account.
Cr Kempton said when he stood in 2010, he always thought of himself being a three-term councillor.
"For me, that is a period in which I could be most effective."
In nine years, it moved from a council just doing its duty to one which "looked more readily to what it could do", he said.
Chairman Stephen Woodhead said he was likely to put his name forward one more time.
However, he indicated he might not go for the chairman role he had held for three terms.
"After nine years as chairperson, it's probably time for a change for the good of the organisation."
Cr Bell said he was undecided and would make his mind up at the end of May.
He previously decided to not run, but many people contacted him asking him to stand again so he would give it some thought.
Cr Deaker said he was undecided and would make his mind up in July or August.
Cr Scott said he was undecided, but leaning towards standing.
"What's required at the table is a balance of experienced and new."
Cr Robertson said she loved her work at the council and wanted to continue to contribute.
"Change is really healthy and I encourage those with new skills and passion for Otago to stand."
Cr Noone said, as a first-term regional councillor, he was "definitely" interested in continuing his work.
"I just feel that a lot of work is to be done but I feel I can add value."
Cr Laws indicated last year he would run again.
New councillors would be good for the organisation, which required some "significant reform" in governance, he said.
Cr Hope was unable to be reached, but had previously indicated she would run again.
None of the councillors running explicitly expressed interest in chairing the council.
