"a foolproof identification system"
"the unfailing sign of an amateur"
"an unfailing test"
"an unfailing source of good stories"
"a subject of unfailing interest"
"unfailing loyalty"
"unfailing good spirits"
"unflagging courtesy"
Impractically dressed..because of her unfailing optimism about the weather.
出自: M. Roberts
His..unfailing politeness made him much admired.
出自: S. Hastings