| well-established(adjective, strain, firmness, labour, hardiness) |
| fixed(adjective, strong, tough, firm, stable) |
| long-lived(adjective, continue, persistent, continuing, recurrent) |
| perennial(adjective, continue, constant, continuous, enduring) |
| immutable(adjective, calm, strong, secure, firm) |
| long(adjective, time, great, deep, high) |
| unchanging(adjective, firm, certain, steady, stable) |
| unending(adjective, persistent, constant, current, continuous) |
| chronic(adjective, fixed, persistent, constant, current) |
| endless(adjective, certain, persistent, constant, reliable) |
| indestructible(adjective, strong, tough, stable, sturdy) |
| unceasing(adjective, persistent, constant, continuous, endless) |
| continual(adjective, certain, stable, persistent, constant) |
| interminable(adjective, persistent, constant, continuous, endless) |
| unchangeable(adjective, calm, strong, solid, steady) |
| undying(adjective, continuous, enduring, permanent, everlasting) |
| unwavering(adjective, calm, strong, firm, solid) |
| ceaseless(adjective, certain, persistent, constant, reliable) |
| continuous(adjective, certain, fixed, persistent, constant) |
| immortal(adjective, perpetual, imperishable) |