all-night vs nightlong

all-night and nightlong both are adjectives.

Word	Noun	Adjective	Verb	Adverb
all-night	No	Yes	No	No
nightlong	No	Yes	No	No

As adjectives, all-night and nightlong are synonyms defined as:

all-night and nightlong: lasting, open, or operating through the whole night

Other synonyms of all-night include overnight.

all-night (adjective)	nightlong (adjective)
lasting, open, or operating through the whole night	lasting, open, or operating through the whole night