| persisting(adjective, determined, steady, stable, resolute) |
| sustained(adjective, persistent, constant, continuous, unyielding) |
| uniform(adjective, steady, regular, persistent, even) |
| ageless(adjective, lasting, permanent, everlasting, unending) |
| changeless |
| continuing(adjective, strong, firm, determined, steady) |
| enduring(adjective, determined, steady, stable, resolute) |
| insistent |
| remorseless(adjective, hard, cruel, persistent, constant) |
| straight(adjective, continuous, continual, nonstop) |
| stubborn |
| timeless(adjective, continue, steady, constant, lasting) |
| unintermitting(perseverance, continuity, diuturnity) |
| untiring(adjective, determined, persevering) |
| around-the-clock(adjective, continue, continual) |
| even(verb, adjective, sound, steady, regular) |
| habitual(adjective, steady, regular, persistent, even) |
| hard(adjective, tough, harsh, cruel, grim) |
| industrious |
| obstinate |