Terms for subject Cliche / convention containing lifetime

English	Russian
it's a once-in-a-lifetime experience	такое бывает только раз в жизни (ART Vancouver)
once-in-a-lifetime	уникальнейший (“This find is truly a once-in-a-lifetime discovery—the sort of thing you read about in textbooks and not something you expect to see coming out of the ground in front of you,” says Mortimer in a statement. -- уникальнейшая находка smithsonianmag.com ART Vancouver)