THESAURUS
unfailing
abiding, assiduous, calculable, certain, changeless, consistent, constant, continuing, dependable, devoted, diligent, dogged, durable, enduring, faithful, faithworthy, fast, firm, fixed, frozen, immobile, immutable, inalterable, indefatigable, indomitable, industrious, insistent, intact, invariable, invincible, inviolate, lasting, loyal, marble-constant, never-tiring, obstinate, patient, patient as Job, permanent, perpetual, perseverant, persevering, persistent, persisting, pertinacious, plodding, plugging, predictable, preoccupied, quiescent, rapt, relentless, reliable, remaining, resolute, rigid, secure, sedulous, single-minded, sleepless, slogging, solid, sound, stable, static, stationary, staunch, staying, steadfast, steady, stubborn, substantial, sure, surefire, sustained, tenacious, tireless, torpid, true, true-blue, trustworthy, trusty, unabating, unaltered, unchangeable, unchanged, unchanging, unchecked, unconquerable, undaunted, undestroyed, undiscouraged, undrooping, unfading, unfaltering, unflagging, unflinching, unintermitting, uninterrupted, unnodding, unrelaxing, unrelenting, unremitting, unshifting, unsleeping, unswerving, untiring, unvaried, unvarying, unwavering, unwearied, unwearying, unwinking, utterly attentive, weariless, well-founded, well-grounded
ROGET THESAURUS
unfailing
Permanence
N
permanence, stability, quiescence, obstinacy, permanence, persistence, endurance, durability, standing, status quo, maintenance, preservation, conservation, conservation, law of the Medes and Persians, standing dish, stable, persisting, permanent, established, unchanged &c (change), renewed, intact, inviolate, persistent, monotonous, uncheckered,
unfailing, undestroyed, unrepealed, unsuppressed, conservative, qualis ab incepto, prescriptive, stationary, in statu quo, for good, finally, at a stand, at a standstill, uti possidetis, without a shadow of turning, esto perpetua, nolumus leges Angliae mutari, j'y suis et j'y ereste.