The curfew will be "reviewed as needed," said Gen. James Thurman in issuing the order, Stars and Stripes reported Thursday.
The order replaces a similar one issued in December 2011 that said the curfew would be reviewed quarterly.
Thurman wrote the curfew was "imposed due to operation and mission-readiness requirements."
"I expect USFK will maintain an appropriate state of awareness and mission preparedness for a significant period," he said.
The curfew prohibits the 28,500 U.S. service members in South Korea from being in off-base establishments between 1 a.m. and 5 a.m. daily.
A previous commander lifted a nine-year-old curfew in July 2010, but Thurman reinstated it three months later after a series of incidents, including two high profile rape cases, involving U.S. service members.