From watchful +‎ -ness.

watchfulness (countable and uncountable, plural watchfulnesses)

1. The state or quality of being watchful; alertness, vigilance or wakefulness.

   Continuous watchfulness is maintained around the clock.

   • 1665, Robert Hooke, Micrographia‎^[1], Preface:

     The first thing to be undertaken in this weighty work, is a watchfulness over the failings and an inlargement of the dominion, of the Senses.

   • 1784, Samuel Johnson, letter addressed to Mr. Langton dated 25 August, 1784, cited in James Boswell, The Life of Samuel Johnson, London: Charles Dilly, 1791, Volume 2, p. 545,^[2]

     Nights of watchfulness produce torpid days […]

   • 1896, H[erbert] G[eorge] Wells, “chapter 9”, in The Island of Doctor Moreau (Heinemann’s Colonial Library of Popular Fiction; 52), London: William Heinemann, →OCLC; republished as The Island of Doctor Moreau: A Possibility, New York, N.Y.: Stone & Kimball, 1896, →OCLC, page 82:

     Every dark form in the dimness had its ominous quality, its peculiar suggestion of alert watchfulness.

   • 1944, Neville Shute, chapter 4, in Pastoral, London: Heinemann:

     The steady rhythm of the engines, the fact that he had been sleeping badly, the boredom of a flight that he had done so many times before and did not want to do again, the long humiliation and unhappiness that was always in the background of his mind, all fought against his watchfulness.

• watchful