"Last muster was put off and put off, because the choppers couldn't fly," Mr Waara said.
This year it's been brought forward to April 26, weather permitting.
The change means Kaimanawa Heritage Horses has less time than usual to find homes for the mustered horses.
There are expected to be 100 this year, and they will be slaughtered if no one wants them.
Mr Waara said the horses were in better condition in recent years because there was more food for them in winter.
"It's actually doing good keeping the numbers down," he said.
"It's just a pity that homes can't be found for all of them."
Mr Waara was one of 12 people who took on the training of two stallions in the Kaimanawa Stallion Challenge last year.
He said they both became really good, quiet horses.
"They are wild animals but they can be trained."
People taking the horses on needed to know how to train them, and they also required a secure yard.
"They've got to have really good yards to hold them so they can work with them. Otherwise they will go straight through the fence because they're really wild," said Mr Waara.