Definition of "unfailing"

There is an unfailing charm about his novels, an unwearing freshness.

1894, Harper's New Monthly Magazine, volume 89, number 534, page 787

It is a work of love, made in difficult times at complex locations, with the unfailing support of dozens of brilliant professional people.

2021 June 30, Tim Dunn, “How we made... Secrets of the London Underground”, in RAIL, number 934, page 51