(n.) Very durable; lasting; continuing long.

abiding age-long aged ageless ancient antique ceaseless chronic coeternal constant continual continuing continuous dateless diuturnal durable endless enduring eternal eterne ever-being ever-durable ever-during evergreen everlasting everliving hardy illimitable immemorial immutable incessant indestructible infinite interminable intransient inveterate lasting long-lasting long-lived long-standing long-term longeval longevous macrobiotic never-ceasing never-ending nonstop nonterminating nonterminous of long duration of long standing olamic perduring perennial permanent perpetual persistent persisting remaining sempervirent sempiternal stable staying steadfast steady timeless tough unceasing unending unfading unintermitting uninterrupted unremitting vital without end