1. uninterrupted in time and indefinitely long continuing

    e.g. the ceaseless thunder of surf
           in constant pain
           night and day we live with the incessant noise of the city
           the never-ending search for happiness
           the perpetual struggle to maintain standards in a democracy
           man's unceasing warfare with drought and isolation
           unremitting demands of hunger

    Synonym: ceaselessconstantincessantnever-endingperpetualunremitting

2. continuing forever or indefinitely

    e.g. the ageless themes of love and revenge
           eternal truths
           life everlasting
           hell's perpetual fires
           the unending bliss of heaven

    Synonym: agelessaeonianeonianeternaleverlastingperpetualunending