Synonyms of longstanding

1 Syllable

old

2 Syllables

yearlong, undying, long-term, stable, constant, endless, lasting, longterm

3 Syllables

durable, perennial, continuing, perpetual, deep-rooted, deep-seated, eternal, continual, abiding, forever, persisting, lifelong, permanent, incessant, unceasing

4 Syllables

unremitting, indelible, everlasting, perdurable

5 Syllables

longitudinal, indissoluble, inexpungible, inexhaustible