lifetime vs period of time

lifetime and period of time both are nouns.

Word	Noun	Adjective	Verb	Adverb
lifetime	Yes	No	No	No
period of time	Yes	No	No	No

As nouns, period of time is a hypernym of lifetime; that is, period of time is a word with a broader meaning than lifetime:

lifetime: the period during which something is functional (as between birth and death)
period of time: an amount of time

Other hypernyms of lifetime include period, time period.

lifetime (noun)	period of time (noun)
the period during which something is functional (as between birth and death)	an amount of time