Elsa
As a fictional character, Elsa's longevity depends entirely upon corporate decisions regarding intellectual property exploitation. The Frozen franchise, whilst remarkably successful, faces the inevitable entropy of cultural relevance. Analysis of Disney Princess merchandise trends suggests that character popularity typically peaks within five to seven years of theatrical release before declining to baseline levels.
Elsa's continued relevance requires sustained investment in new content, theme park attractions, and merchandise refreshment. Should Disney's corporate priorities shift, her cultural presence would diminish accordingly, subject to the same forces that relegated previous Disney properties to nostalgic memory.
Monday
Monday's longevity is assured by the fundamental structure of human timekeeping. Since the Babylonians established the seven-day week in approximately 2350 BCE, Monday has persisted through the rise and fall of countless civilisations, empires, and entertainment franchises. It witnessed the construction and subsequent ruin of ancient Rome, the entire medieval period, and the complete arc of the British Empire.
Barring a complete reformation of the Gregorian calendar system, Monday will continue its weekly occurrence until such time as human civilisation itself ceases to track the passage of days. This represents a longevity measured not in decades but in millennia, a temporal permanence that no fictional character, however beloved, can hope to match.