aging (or ageing), mature

antiquated, archaic, archaistic, dated, fusty, geriatric, medieval (also mediaeval), moldy, Noachian, obsolete, outmoded, out-of-date, passé

old-fashioned, old-time, old-world, retro, vintage

durable, enduring, lasting, long-lived, permanent

ageless, hallowed, time-honored, timeless, time-tested, timeworn, traditional, tried, tried-and-true

classic, classical

prehistoric (also prehistorical), primeval, primordial