long haul vs period of time

long haul and period of time both are nouns.

Word	Noun	Adjective	Verb	Adverb
long haul	Yes	No	No	No
period of time	Yes	No	No	No

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

Other hypernyms of long haul include period, time period.

long haul (noun)	period of time (noun)
a journey over a long distance	an amount of time
a period of time sufficient for factors to work themselves out