| durable(adjective, tough, continue, stable, enduring) |
| long-lived(adjective, continue, familiar, established, hardened) |
| permanent(adjective, tough, continue, sturdy, constant) |
| long-standing(adjective, continue, hardened, existing, confirmed) |
| enduring(adjective, tough, continue, familiar, sturdy) |
| lasting(adjective, tough, continue, sturdy, constant) |
| perennial(adjective, continue, familiar, constant, enduring) |
| persistent(adjective, tough, continue, sturdy, constant) |
| continuing(adjective, continue, familiar, established, hardened) |
| abiding(adjective, tough, continue, sturdy, enduring) |
| tough |
| constant(adjective, tough, familiar, sturdy, enduring) |
| eternal(adjective, continuous, enduring, lasting, permanent) |
| indestructible(adjective, tough, stable, sturdy, constant) |
| stable(adjective, tough, sturdy, constant, enduring) |
| strong |
| immutable(adjective, stable, constant, enduring, lasting) |
| inveterate(adjective, familiar, established, hardened, confirmed) |
| lifelong(adjective, familiar, established, hardened, lasting) |
| old(adjective, continue, familiar, established, hardened) |