| ceaseless(fixed, persistent, continuous, lasting, continuing) |
| confirmed(verb, fixed, persistent, continuous, hardened) |
| deep-rooted(adjective, fixed, persistent, hardened, lasting) |
| deep-seated(fixed, persistent, continuous, hardened, lasting) |
| endure |
| ever-present(fixed, persistent, continuous, lasting, continuing) |
| forever(permanent, long-term) |
| habitual(fixed, persistent, continuous, hardened, lasting) |
| in for the long haul(expression, idiom, permanent, long-term) |
| inborn(fixed, persistent, continuous, lasting, continuing) |
| inbred(fixed, persistent, continuous, hardened, lasting) |
| incurable(fixed, persistent, continuous, hardened, lasting) |
| indelible(permanent, long-term) |
| ineradicable(fixed, persistent, continuous, hardened, lasting) |
| inexhaustible(permanent, long-term) |
| inexpungible(permanent, long-term) |
| ingrained(fixed, persistent, continuous, hardened, lasting) |
| intransient |
| intransitive |
| lingering(fixed, persistent, lasting, remaining, chronic) |