Both sentences are fairly tortured. "extended period" and "long period" are fine by themselves, but using them before a noun to modify the noun can be awkward (also, if you did do it, a hyphen would be needed in "long-period" and "extended-period"). Compared with "long period", "extended period" is a more elaborate phrasing and can suggest that a period of time has been made longer than usual or than expected.
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CalifJimIf I may suggest a more idiomatic way to say those:It takes a long time to make a car.It takes a long time to travel from China to the U.S.Indeed.