At that point they find they no longer have anything in common and want to "do their own thing", says divorce lawyer Jeremy Sutton.
By law, couples have to separate for two years before they can file for divorce on the grounds of irreconcilable difference.
Sutton, a divorce lawyer for 24 years, said that meant divorces were usually well considered.
"I think it's there to give people time out before the next one; to give them some breathing space.
"Society probably doesn't think it's a good idea to divorce one person and move on to the next one straight away. I think it's a conservative English attitude."
Data from the Department of Internal Affairs shows dropping divorce rates -- tied to lower rates of marriage.
In 1984, there were 28.15 marriages for every 1000 citizens, but by 2014 that had dropped to 11.57 marriages.
Peter McMillan, co-founder of the Imago Institute for Relationships, said the time of year couples found most difficult and sought his help the most was mid-January after Christmas and New Year's Eve.
"It's two things, from mid-November until Christmas, things get pretty stressful. And secondly, it's also a time when people stop and reflect on what they want. Then they realise that perhaps things aren't as good in their relationship as they were hoping they would be."
The second peak for relationship counsellors is mid-winter when it's darker, colder and people get "weighed down" more easily, he said.
McMillan said if relationships were to survive, communication was important. "If you're struggling, get some help," he said.
Couples should also identify their top values and make sure their partner knows and respects them. It was also important not to leave it too long before confronting issues.
Third time a charm for lovebirds
Stephen Harrison knows his third marriage will stick because of what he's learned from his past failed relationships and the work he and his wife, Juanita Theron, have put into their marriage.
The 53-year-old met Theron, 49, four-and-a-half years ago and they decided to make it legal after 18 months.
Harrison's first marriage lasted 13 years and he has three children from that relationship.
His second lasted seven years. Theron has also had other marriages and has a child. However, none of the couple's children still live in the Wellington couple's home.
Before they married, the couple went to counselling to learn how to communicate.
Harrison said he'd also learned from his previous marriages and brought those lessons to his new relationship.
"Now I'm in a relationship where we are able to bring up things and work through the issues."
