indefatigability

From in- +‎ de- +‎ fatigue +‎ -ability.

indefatigability (countable and uncountable, plural indefatigabilities)

1. the state of being indefatigable; tirelessness; persistence; stamina.
   • 1982 April 17, Michael Bronsky, “What Are These Men Really Selling and Whom Are They Trying to Fool”, in Gay Community News, page 6:

     The absurdity of each year's changing fashions attest not so much to the gullibility of the buyers as to the indefatigability of designers to make a quick buck.

• indefatigableness

• indefatigable