| dateless(adjective, permanent, everlasting, unending, undying) |
| indelible(adjective, great, firm, extraordinary, true) |
| lengthy(adjective, great, deep, high, remote) |
| tenacious(adjective, tough, firm, true, fixed) |
| tough(adjective, calm, strong, solid, substantial) |
| unfading(stable, fixed, constant, vast, enduring) |
| unfaltering(adjective, persevering) |
| unflagging(adjective, persevering) |
| unrelenting(adjective, certain, persistent, constant, reliable) |
| ageless(adjective, fixed, permanent, unchangeable, everlasting) |
| continue |
| deep(adjective, great, high, remote, long) |
| evergreen |
| existing(verb, adjective, established, permanent, existing) |
| imperishable(adjective, constant, enduring, permanent, durable) |
| indefatigable(adjective, continuous, persevering) |
| ineradicable(adjective, fixed, persistent, remaining, chronic) |
| long-drawn-out(adjective, great, high, long, extended) |
| monumental(adjective, great, extraordinary, outstanding, remarkable) |
| overlong(adjective, great, high, long, extended) |