lifespan vs life-time

lifespan and life-time both are nouns.

Word	Noun	Adjective	Verb	Adverb
lifespan	Yes	No	No	No
life-time	Yes	No	No	No

As nouns, lifespan and life-time are synonyms defined as:

lifespan and life-time: the period during which something is functional (as between birth and death)

Other synonyms of lifespan include life, lifetime.

lifespan (noun)	life-time (noun)
the period during which something is functional (as between birth and death)	the period during which something is functional (as between birth and death)