long-familiar vs well-known

long-familiar and well-known both are adjectives.

Word	Noun	Adjective	Verb	Adverb
long-familiar	No	Yes	No	No
well-known	No	Yes	No	No

As adjectives, long-familiar and well-known are synonyms defined as:

long-familiar and well-known: frequently experienced; known closely or intimately

long-familiar (adjective)	well-known (adjective)
frequently experienced; known closely or intimately	frequently experienced; known closely or intimately
	widely or fully known