Spending on them regularly tops the family's shopping bill. Where she now shopped depended on what store offered the best deal.
"Any reduction in price can make a big difference," Wilmshurst told the Herald on Sunday.
"I keep an eye out for good specials, then I might buy four boxes at once. It's great news for parents that retailers are competing."
It's not just Kiwi families that are benefiting from the competition.
Massey University senior marketing lecturer Andrew Murphy said slashing prices would give major supermarket chains a lift in business.
The ploy was designed to lure parents into the store.
"If the retailer is cutting their margin they will be expecting they can gain something," he said.
"If it's a product the customer knows the price of, thinks is a good deal and makes a special trip to acquire, the retailer hopes that while they're there they are buying things that are not deeply discounted."
Nappies were an effective tool to attract shoppers into the store as families were keenly aware of the regular price. With other commonly purchased household items it was harder to judge the discount, he said.
Murphy's view was backed by Rochelle Gribble, editor of Kiwi Families website. She said it was not uncommon for Facebook parenting groups to be filled with posts from parents looking for the best price for nappies.
"They might say, Countdown has Treasures on special this week, or where can I get Huggies cheap?
"When the supermarket drops a few dollars off a packet it does make a big difference.
"If you are on a fixed income every cent counts."
Countdown's general manager of merchandise, Steve Donohue, said the disposable nappy market was one of the most competitive for supermarket chains.
"Parents choose nappies based on price and quality, and traditionally prices have changed week to week as different products go on short-term promotions." Supermarket chains were aware that parents stockpiled nappies depending on hot deals.
In a bid to cash in, Countdown had permanently cut the price of Homebrand nappies from $19 to $15 for 44-60 pack nappies.
That would save customers overall $1m a year.
It has also introduced a price drop on Treasures convenience packs.
Market moves from Foodstuffs, which handles the New World, Pak'nSave and Four Square brands, included special promotions including "baby week".
The company's corporate PR director, Antoinette Laird, said the promotion saw "prices slashed across the entire baby category".