Jones and Company Funeral Services director Chris Andrews said the company had just under 100 urns of ashes stored with the oldest going back about 15 years.
Every six months staff tracked down the families, sent letters to each and kept records of who had replied and who had not.
"That system of just prompting people seems to work for us," he said. "We still carry ashes but nowhere near the amount we had in the past."
Some people asked the company to hold the ashes indefinitely, he said.
"Some families say, 'please hold Dad's ashes until Mum passes away'."
Legacy Funerals director Mike Savage said he had about 80 urns of ashes in storage with the oldest ones being from about 1995.
"People forget. They move on with their lives and forget that their loved one is here.
"It's not intentional, it's just the way it is."
Mr Savage said staff tried to contact the families about once a year to find out what they wanted to do with the ashes.
"Most of the time their reaction is, 'Oh goodness. We overlooked it'.
"People think, 'Aunty Joan, we'll ask her to pick them up' and they forget to ask her and Aunty Joan moves on and they just forget."
Tony Hope of Hope Family Funerals said they had built up a collection of about 50 urns waiting to be picked up since they started the business about six years ago.
It was not a big problem as most people remembered to collect their loved ones, he said.
"Sometimes people just aren't emotionally ready to come in and pick them up, sometimes people are going overseas or they'd rather not have them in their house."