How many letters does the top answer for “the state of being everlasting; endless duration; indefinite duration.” have?

The most common answer is everlastingness (15 letters).

Crossword clue: the state of being everlasting; endless duration; indefinite duration.

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

everlastingness 15 letters web-def

the property of lasting forever

the state of being endless. 50% similar → interminableness