| perennial(adjective, constant, endless, indefinite, lasting) |
| sempiternal(adjective, eternal) |
| abiding(adjective, lasting, permanent, everlasting, eternal) |
| enduring(adjective, eternal) |
| unlimited(adjective, endless, infinite, boundless, incessant) |
| continual(adjective, continue, constant, incessant, eternal) |
| continuous(adjective, continue, steady, constant, endless) |
| immemorial(adjective, vast, lasting, infinite, permanent) |
| incessant(adjective, continue, steady, persistent, constant) |
| imperishable(adjective, vast, lasting, permanent, everlasting) |
| indestructible(adjective, lasting, permanent, everlasting, eternal) |
| limitless(adjective, endless, infinite, boundless, incessant) |
| time-honoured |
| unchanged |
| unremitting(adjective, continue, steady, constant, lasting) |
| around-the-clock(adjective, continue, continual) |
| boundless(adjective, continuous, endless, infinite, everlasting) |
| customary |
| long-lived |
| persistent(adjective, continue, steady, constant, continuous) |