nightlong vs all-night

nightlong and all-night both are adjectives.

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

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

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

Other synonyms of nightlong include overnight.

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