National is well aware there could be a very high level of advance votes cast in the September election, Deputy Prime Minister Paula Bennett says.
She told delegates at the party's annual conference on Saturday there were 97 days to go but only 79 before advance votes could be cast.
More than 30 percent of the votes cast in 2014 were advance votes, and Ms Bennett later told reporters she believed the figure could top 50 percent this time.
"It changes the dynamics of the campaign, and when you say things and make announcements," she said.
"You can't wait until the last few weeks."