forever vs incessantly

forever and incessantly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
forever	No	No	No	Yes
incessantly	No	No	No	Yes

As adverbs, forever and incessantly are synonyms defined as:

Other synonyms of forever include always, constantly, perpetually.

forever (adverb)	incessantly (adverb)
for a limitless time	invariably
for a very long or seemingly endless time	with unflagging resolve
invariably