New Zealand has decided to revert to 10-year passports in 2016 following a change to five-year travel documents last decade, with critics saying this longer validity increases convenience without impacting on security."The 10-year validity period gives greater convenience to most adult passport holders, as they will need to renew their passport less frequently," Internal Affairs Minister Peter Dunne said in a statement on Monday.Dunne added however that because a child's appearance can change significantly over time, the child passport will remain valid for five years as is international convention. The country introduced five-year passports in 2005.Prime Minister John Key confirmed the new passports will cost $180 compared with $135 to renew a current five-year passport.Key defended the cost, saying it that by law the fees were based on a cost-recovery basis and the Government made no extra revenue from it.