WordNet sense 1 (continuing forever or indefinitely):

ageless, everlasting, perpetual, unceasing, unending, aeonian, eonian

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

lasting, permanent

WordNet sense 3 (tiresomely long; seemingly without end):

endless, interminable

WordNet sense 4 (primarily temporal sense; being or indicating a relatively great or greater than average duration or passage of time or a duration as specified):

long