The Navy's only tanker, the HMNZS Endeavour, has completed its last long-term deployment before it is decommissioned.

A full crew of 52 returned home to the Devonport naval base in Auckland this morning, after more than four months working around South East Asia - Brunei, Singapore, Cambodia - and Australia.

The Navy's second-largest ship, the Endeavour was built in 1988 and has travelled the equivalent of earth to the moon and back twice since - 1.51 million kilometres - but after nearly 30 years has come to the end of its life.

Boots Lyes, a Navy engineer since 1979, was on one of the Endeavour's first deployments in 1988 and has tended her engines for 14 years cumulatively.

"When we first got it we'd just turn the key at four in the afternoon and not come back til eight 'o clock in the morning. It's just that reliable when it's new," he said.

"But as she's got older and older, it takes more maintenance, we've got more crew on than when we were new, about 6 or 7 engineers more because there's more maintenance to keep her going."

The Endeavour will be decommissioned in December, and either sold, scrapped, or sunk.

It will be replaced by the HMNZS Aotearoa in 2020 at a cost of just under $500 million. The Aotearoa will be the Navy's largest ship.