WordNet sense 1 (continuing forever or indefinitely):

ageless, eternal, everlasting, perpetual, unending, aeonian, eonian

WordNet sense 2 (continuing or enduring without marked change in status or condition or place):

lasting, permanent

WordNet sense 3 (uninterrupted in time and indefinitely long continuing):

ceaseless, constant, incessant, unremitting, never-ending

WordNet sense 4 (continuing in time or space without interruption):

continuous, uninterrupted